Ammonia coal coupling ultra-low nitrogen combustion system and method for vertical pulverized coal boiler

Abstract

The ammonia coal coupling ultra-low nitrogen combustion system comprises a boiler body, and the boiler body is sequentially provided with a lower-layer combustion area, a middle-layer combustion area and an upper-layer combustion area from bottom to top; lower-layer combustors are arranged on the side wall and / or four corners of the lower-layer combustion area, middle-layer combustors are arranged on the side wall and / or four corners of the middle-layer combustion area, upper-layer combustors are arranged on the side wall and / or four corners of the upper-layer combustion area, ammonia-coal co-combustion combustors are adopted as the lower-layer combustors and the middle-layer combustors, and pure ammonia combustors are adopted as the upper-layer combustors; the middle-layer combustor and the lower-layer combustor both adopt the ammonia-coal co-combustion staged oxygen supply and staged combustion principle, stable ammonia flames are formed by means of the rapid ignition and stable combustion characteristics of ammonia, the flames are rich in active reduction components and residual ammonia, nitric oxide generated in the coal combustion process can be effectively reduced, and the combustion efficiency is improved. And the upper layer combustor is used for reducing NOx generated by combustion of the middle layer and the lower layer, so that the content of NOx in the flue gas is further reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia-coal combustion, and particularly to a vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system and a combustion method. Background Art

[0002] China is a major coal-producing country. Coal has a long history of being used as a fuel for combustion to provide heat for industrial and civil use. Pulverizing coal increases the specific surface area, facilitating mixing with combustion-supporting air, which is beneficial for the ignition and complete combustion of coal and improves energy utilization efficiency. Thermal power plants or industrial boilers generally adopt the pulverized coal combustion method to heat water or steam. As a solid fuel, coal is more difficult to ignite and burn compared to liquid and gas fuels. When the boiler load and temperature are relatively low, liquid or gas fuels are often needed to assist in ignition and stabilize the flame. For example, during boiler ignition or when there are peak shaving requirements, diesel or plasma igniters are used for ignition or combustion support.

[0003] Since coal is a high-carbon fuel, a large amount of carbon dioxide is generated during combustion. Therefore, it is urgent to develop efficient and stable combustion technologies for the mixed combustion of coal with low-carbon and zero-carbon fuels, and continuously increase the proportion of zero-carbon fuels.

[0004] The present invention focuses on the ammonia-coal mixed combustion technology for thermal power plants and industrial boilers, especially the combustion method of vertical boilers. Conventional pulverized coal combustion in boilers is often accompanied by a large amount of nitrogen oxide (NOx) emissions, and the combustion of ammonia also produces a large amount of nitrogen oxides, which has a significant impact on the environment. To address this issue, various low-nitrogen combustion technologies have been developed in the industry, but these technologies still have deficiencies in terms of combustion stability and fuel burnout rate. Therefore, developing a new combustion method that can effectively reduce NOx emissions while ensuring the stability of ammonia-coal mixed combustion and the complete combustion of fuel has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system and a combustion method to solve one or more technical problems existing in the prior art, and at least provide a beneficial alternative or create conditions.

[0006] The technical solutions adopted to solve the above technical problems are as follows: The present invention provides a vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system, including a boiler body with a slag discharge outlet at the bottom, and a flue gas discharge outlet at the top of the boiler body. The boiler body is sequentially provided with a lower combustion zone, a middle combustion zone, and an upper combustion zone from bottom to top; the side walls and / or four corners of the lower combustion zone are provided with lower burners, the side walls and / or four corners of the middle combustion zone are provided with middle burners, and the side walls and / or four corners of the upper combustion zone are provided with upper burners. Both the lower burners and the middle burners adopt ammonia-coal co-combustion burners, and the upper burners adopt pure ammonia burners; the ammonia-coal co-combustion burner is provided with an ammonia gas channel, a primary combustion-supporting air channel, a pulverized coal air channel, a secondary combustion-supporting air channel, an ammonia gas combustion channel, an ammonia-coal mixed combustion channel, and a first igniter. The ammonia gas channel and the primary combustion-supporting air channel are both communicated with the ammonia gas combustion channel, the first igniter is arranged in the ammonia gas combustion channel, and the ammonia gas combustion channel, the pulverized coal air channel, and the secondary combustion-supporting air channel are all communicated with the ammonia-coal mixed combustion channel.

[0007] The beneficial effects of the present invention are as follows: The nitrogen combustion system is arranged in three layers: upper, middle, and lower. Each layer is provided with fuel and air nozzles, and there is a sufficient vertical distance between layers. The middle combustion zone and the lower combustion zone adopt ammonia-coal co-combustion burners, and the upper combustion zone adopts pure ammonia burners, ensuring the independence of the combustion process of each layer and the stability of the flame structure. Both the middle burners and the lower burners adopt the principle of ammonia-coal co-combustion with staged oxygen supply and staged combustion, and use the fast ignition and stable combustion characteristics of ammonia to form a stable ammonia flame. This flame is rich in active reducing components and residual ammonia, which can effectively reduce the nitrogen oxides generated during coal combustion. By controlling the temperature and the amount of combustion-supporting air, the combustion process is in a state where the excess air coefficient is less than 1 and a suitable reaction temperature environment, further suppressing the generation of NOx. The upper burners adjust the amount of combustion-supporting air to make the upper burner flame in a reducing atmosphere, reducing the NOx generated by the middle and lower layers of combustion, and further reducing the NOx content in the flue gas.

[0008] As a further improvement of the above technical solution, the ammonia-coal co-combustion burner includes a first shell, a second shell, a third shell, and a fourth shell. The third shell is sleeved inside the fourth shell, the second shell is sleeved inside the third shell, the first shell is sleeved inside the second shell, the first igniter is arranged in the first shell, the ammonia gas channel is formed between the side wall of the first igniter and the first shell, the primary combustion-supporting air channel is formed between the first shell and the second shell, the ammonia gas combustion channel is formed inside the second shell, the pulverized coal air channel is formed between the second shell and the third shell, the secondary combustion-supporting air channel is formed between the third shell and the fourth shell, and the ammonia-coal mixed combustion channel is formed inside the fourth shell.

[0009] As a further improvement of the above technical solution, the ammonia channel, the primary combustion air channel, the pulverized coal air channel, and the secondary combustion air channel are all annular channels.

[0010] As a further improvement of the above technical solution, at one end of the first housing close to the ammonia combustion channel, there are provided a plurality of first ammonia outlets for spraying ammonia radially along the first housing and a plurality of second ammonia outlets for spraying ammonia axially along the first housing.

[0011] As a further improvement of the above technical solution, the primary combustion air channel is provided with a swirling air outlet structure.

[0012] As a further improvement of the above technical solution, the first igniter is located on the central axis of the first housing.

[0013] As a further improvement of the above technical solution, at one end of the second housing close to the ammonia-coal mixed combustion channel, there is provided a diffusion section, and the diameter of the diffusion section gradually increases along the spraying direction of the flame of the first igniter.

[0014] As a further improvement of the above technical solution, the pure ammonia burner includes a fifth housing, a sixth housing, and a second igniter. The fifth housing is sleeved inside the sixth housing. The second igniter is arranged inside the fifth housing. An ammonia delivery channel is formed between the side wall of the second igniter and the fifth housing. A combustion-supporting air channel is formed between the fifth housing and the sixth housing. The sixth housing is provided with a pure ammonia combustion channel. The ammonia delivery channel and the combustion-supporting air channel are both communicated with the pure ammonia combustion channel.

[0015] As a further improvement of the above technical solution, the second igniter is located on the central axis of the fifth housing.

[0016] The present invention also provides a combustion method, which is applied to the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system described in any one of the above. The combustion method includes: Controlling each layer of burners to introduce corresponding combustion gases and combustion-supporting air and simultaneously controlling each layer of burners to ignite; By adjusting the delivery ratios of the primary combustion-supporting air, ammonia, secondary combustion-supporting air, and pulverized coal air of the lower-layer burners, the temperature of the lower-layer combustion zone is kept lower than 800 °C, and the air excess coefficient is kept below 1; By adjusting the delivery ratios of the primary combustion-supporting air, ammonia, secondary combustion-supporting air, and pulverized coal air of the middle-layer burners, the temperature of the middle-layer combustion zone is kept at a temperature higher than 1000 °C, and the air excess coefficient is kept between 1.1 and 1.3; By adjusting the proportion of combustion-supporting air and ammonia delivery of the upper-layer pure ammonia burner, the temperature of the upper-layer combustion zone is maintained slightly lower than that of the middle-layer combustion zone, and the air excess coefficient is between 0.5 and 0.8. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the drawings and embodiments; Figure 1 FIG. is a schematic cross-sectional view of the structure of one embodiment of the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system provided by the present invention, where the two arrows respectively represent upward and downward directions; Figure 2 FIG. is a schematic side view of the structure of one embodiment of the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system provided by the present invention, where the two arrows respectively represent upward and downward directions; Figure 3 FIG. is a schematic cross-sectional view of the ammonia-coal co-combustion burner of one embodiment of the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system provided by the present invention; Figure 4 FIG. is a schematic cross-sectional view of the pure ammonia burner of one embodiment of the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system provided by the present invention.

[0018] Reference numerals: Boiler body 100, lower-layer combustion zone 101, middle-layer combustion zone 102, upper-layer combustion zone 103, ash discharge outlet 110, flue gas discharge outlet 120; Ammonia-coal co-combustion burner 200, ammonia channel 201, primary combustion-supporting air channel 202, pulverized coal air channel 203, secondary combustion-supporting air channel 204, ammonia combustion channel 205, ammonia-coal mixed combustion channel 206, first housing 210, first ammonia outlet 211, second ammonia outlet 212, second housing 220, diffusion section 221, third housing 230, fourth housing 240, first igniter 250, swirling gas outlet structure 260; Pure ammonia burner 300, ammonia delivery channel 301, combustion-supporting air channel 302, pure ammonia combustion channel 303, fifth housing 310, sixth housing 320, second igniter 330. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] This part will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the drawings. The role of the drawings is to supplement the description of the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be construed as a limitation on the protection scope of the present invention.

[0020] In the description of the present invention, it should be understood that with regard to the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc., it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0021] In the description of the present invention, if there are vocabulary descriptions such as "several", its meaning is one or more, and the meaning of multiple is more than two. Understandings such as greater than, less than, exceeding, etc. do not include the base number, and understandings such as above, below, within, etc. include the base number.

[0022] In the description of the present invention, unless otherwise clearly defined, words such as setting, installation, connection, etc. should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0023] Refer to Figures 1 to 4 , the following embodiments are made for the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system and combustion method of the present invention: In some embodiments, refer to Figure 1 and Figure 2 , the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system includes: A slag discharge port 110 is provided at the bottom of the boiler body 100 for discharging slag from the slag discharge port 110. A flue gas discharge port 120 is provided at the top of the boiler body 100. The flue gas discharge port 120 is connected to a flue gas discharge pipe for discharging flue gas. The boiler body 100 is successively provided with a lower combustion zone 101, a middle combustion zone 102, and an upper combustion zone 103 from bottom to top. Each layer is designed with fuel and air nozzles. There is at least a vertical distance of more than 1 m between the three combustion zones to ensure the independence of each layer of combustion process and form a stable flame structure at the same time. This design helps to achieve uniform combustion of fuel and improve combustion efficiency.

[0024] The side walls of the lower combustion zone 101 are provided with a plurality of lower burners, the side walls of the middle combustion zone 102 are provided with a plurality of middle burners, and the side walls of the upper combustion zone 103 are provided with a plurality of upper burners. Both the lower burners and the middle burners adopt ammonia-coal co-firing burners 200, and the upper burners adopt pure ammonia burners 300. Temperature sensors are provided in the upper combustion zone 103, the middle combustion zone 102, and the lower combustion zone 101. In some other embodiments, for example, in a tangentially fired boiler, a plurality of lower burners may also be located at the corner positions of the lower combustion zone 101, a plurality of middle burners may also be located at the corner positions of the lower-middle combustion zone 102, and a plurality of upper burners may also be located at the corner positions of the upper combustion zone 103, and technical effects such as stable combustion and low NOx can also be achieved. Or in some ultra-large boilers, burners corresponding to each layer of combustion zone are installed at both the corners and the side walls of the boiler body 100; The middle burners and the lower burners adopt the ammonia-coal co-firing staged combustion principle, and utilize the fast ignition and stable combustion characteristics of ammonia to form a stable ammonia flame. This flame is rich in active reducing components and residual ammonia, and can effectively reduce the nitrogen oxides NOx generated during the coal combustion process. By controlling the temperature and the amount of combustion-supporting air, the combustion process is in a state where the excess air coefficient is less than 1 and a suitable reaction temperature environment, further inhibiting the generation of NOx and reducing the nitrogen oxide emissions.

[0025] The upper burners adjust the amount of combustion-supporting air to make the ammonia burner flame in a reducing atmosphere, and reduce the NOx generated by the middle and lower layer combustion, further reducing the NOx content in the flue gas.

[0026] Refer to Figure 3, the ammonia-coal co-firing burner 200 includes a first housing 210, a second housing 220, a third housing 230, a fourth housing 240, and a first igniter 250. The first housing 210, the second housing 220, the third housing 230, and the fourth housing 240 are all cylindrical housings. The first igniter 250 is arranged on the central axis of the first housing 210. The first igniter 250 adopts a high-energy electronic igniter to ensure the ignition reliability of the first igniter 250. An ammonia channel 201 is formed between the outer peripheral walls of the first housing 210 and the first igniter 250. The cross-section of the ammonia channel 201 is annular to ensure the uniform outlet of ammonia. The second housing 220 is sleeved outside the first housing 210. A primary combustion air channel 202 is formed between the first housing 210 and the second housing 220. The third housing 230 is sleeved outside the second housing 220. A pulverized coal air channel 203 is formed between the second housing 220 and the third housing 230. The fourth housing 240 is sleeved outside the third housing 230. A secondary combustion air channel 204 is formed between the third housing 230 and the fourth housing 240. The second housing 220 is also provided with an ammonia combustion channel 205. The fourth housing 240 is also provided with an ammonia-coal mixed combustion channel 206. The primary combustion air channel 202 and the ammonia channel 201 are both communicated with the ammonia combustion channel 205. The ammonia combustion channel 205, the secondary combustion air channel 204, and the pulverized coal air channel 203 are all communicated with the ammonia-coal mixed combustion channel 206. The primary combustion air and ammonia are mixed in the ammonia combustion channel 205 and ignited by the first igniter to form an ammonia combustion flame, and then mixed with the pulverized coal air and secondary combustion air in the ammonia-coal mixed combustion channel 206, and the pulverized coal therein is ignited to form a pulverized coal burner flame. For the requirements of ammonia-coal co-firing in a vertical boiler, the combustion method of using ammonia flame to ignite pulverized coal instead of the existing method of using pulverized coal flame to ignite ammonia is adopted. The high-energy electronic igniter for ammonia fuel installed at the center of the burner ensures the ignition reliability of the ammonia burner. The ammonia burner flame ensures the stable ignition and combustion of low-temperature pulverized coal, making the boiler start more quickly and stably. The design of layered arrangement and staged combustion makes the boiler more adaptable to different load and fuel conditions, enhancing the flexibility and reliability of operation.

[0027] Since the first housing 210, the second housing 220, the third housing 230, and the fourth housing 240 are all cylindrical, the ammonia channel 201, the primary combustion air channel 202, the pulverized coal air channel 203, and the secondary combustion air channel 204 are all annular channels, which is beneficial to the uniform mixing of gases, and valves for controlling the gas flow rate and on-off are provided for regulating the flow rate of each channel. One end of the second housing 220 close to the ammonia-coal mixed combustion channel 206 is provided with a diffusion section 221, and the diameter of the diffusion section 221 gradually increases along the spraying direction of the flame of the first igniter 250. The diffusion section 221 facilitates the diffusion of the flame combustion into the ammonia-coal mixed combustion channel 206.

[0028] To improve the combustion effect of ammonia, a swirling gas outlet structure 260 is provided between the primary combustion air channels 202. The swirling structure 260 includes a swirling base and swirling fan blades, which make the mixing of air and ammonia more uniform. The outlet end of the first housing 210 is provided with a plurality of first ammonia outlets 211 that jet ammonia radially along the first housing 210 and a plurality of second ammonia outlets 212 that jet ammonia axially along the first housing 210. The ammonia from the first ammonia outlets 211 is premixed with the air in the primary combustion air channels 202 and enters the ammonia combustion channel 205, and part of the ammonia from the second ammonia outlets 212 is ignited by the first igniter. The ammonia from the second ammonia outlets 212 directly enters the ammonia combustion channel 205 for combustion.

[0029] By controlling the amount of combustion-supporting air in the lower burner to be in a state where the air excess coefficient is less than 1, the amount of nitrogen oxides generated during its combustion process is very small, and there are a large number of active components and residual ammonia. Such a high-temperature ammonia flame with such components can easily ignite the pulverized coal flame, and the active reducing components in the ammonia combustion flue gas can be used to greatly reduce the nitrogen oxides generated by coal combustion.

[0030] Both the middle burner and the lower burner are ammonia-coal co-combustion burners 200 designed based on the principle of staged combustion of ammonia-coal co-combustion. The fast ignition and stable combustion characteristics of ammonia are used to form a stable ammonia flame, and then the active reducing ammonia flame is used to ignite the pulverized coal and inhibit the fuel-type and thermal-type nitrogen oxides generated by the combustion of pulverized coal. Since the combustion-supporting air is mixed and burned in stages, especially the ammonia combustion flame in the middle of the burner is anoxic combustion, which can greatly reduce the amount of nitrogen oxides generated. The hydrogen molecules, residual ammonia, and carbon monoxide formed during incomplete combustion in the early combustion process will enter the combustion zone at the flame tail by the secondary combustion-supporting air and mix with it and finally burn completely at an appropriate temperature.

[0031] In addition, the furnace temperature at the flame outlet of the lower ammonia-coal co-combustion burner 200 is controlled at a lower temperature, i.e., lower than 800 °C, and the air excess coefficient is maintained below 1, which can further utilize the staged combustion of low-temperature and low-oxygen ammonia-coal co-combustion to help further reduce the generation of fuel-type and thermal-type NOx during the combustion of ammonia and pulverized coal.

[0032] The middle burner is located above the combustion flue gas layer of the lower burner, and a method of staged combustion of high-temperature and low-oxygen ammonia-coal co-combustion can be adopted on the basis of the existing flue gas environment in the furnace. For example, the combustion flame environment of the middle burner ammonia-coal co-combustion burner 200 is maintained at a higher temperature, which can be higher than 1000 °C, and the air excess coefficient is maintained between 1.1 and 1.3. By further utilizing the ignition advantage of ammonia, it promotes the full combustion of pulverized coal at high temperature. On the one hand, it can improve the fuel burnout rate, and on the other hand, it helps to reduce the generation of fuel-type and thermal-type NOx simultaneously.

[0033] Refer to Figure 4, in the upper combustion zone 103, a pure ammonia burner 300 is adopted. The pure ammonia burner 300 includes a fifth housing 310, a sixth housing 320, and a second igniter 330. Both the fifth housing 310 and the sixth housing 320 are cylindrical housings. The fifth housing 310 is sleeved inside the sixth housing 320. The second igniter 330 is arranged inside the fifth housing 310. The second igniter 330 is located on the central axis of the fifth housing 310, which is beneficial to fully ignite ammonia. An ammonia delivery channel 301 is formed between the side wall of the second igniter 330 and the fifth housing 310. A combustion-supporting air channel 302 is formed between the fifth housing 310 and the sixth housing 320. The sixth housing 320 is provided with a pure ammonia combustion channel 303. Both the ammonia delivery channel 301 and the combustion-supporting air channel 302 are communicated with the pure ammonia combustion channel 303.

[0034] The structure of the pure ammonia burner 300 is the same as the intermediate ammonia combustion structure principle in the lower burner and the middle burner. Only during operation, the amount of combustion-supporting air needs to be reduced to make the flame of the ammonia burner in a reducing atmosphere. The combustion flame environment of the upper pure ammonia burner 300 is maintained at a moderately high temperature, that is, slightly lower than the flame environment temperature of the middle burner. The air excess coefficient is less than 1 and is between 0.5 and 0.8, which is convenient for reducing NOx in the flue gas of the middle and lower combustion flames.

[0035] The burners arranged in the upper layer can, on the one hand, adjust the overall heat distribution of the boiler to make it more reasonable; on the other hand, further reduce NOx in the flue gas and achieve good NOx reduction effect.

[0036] In addition, in the combustion system of this embodiment, the heat distribution can also be optimized and the fuel burnout rate can be improved: The middle burner utilizes the flue gas environment generated by the lower burner and adopts a high-temperature and low-oxygen ammonia-coal co-combustion staged combustion method, which promotes the full combustion of pulverized coal at high temperature and improves the fuel burnout rate. The arrangement of the upper burner not only adjusts the overall heat distribution of the boiler to make it more reasonable, but also further reduces NOx in the flue gas through its reducing flame, achieving a double improvement in heat utilization and environmental protection benefits.

[0037] The present invention also provides an embodiment of a combustion method, which is applied to the vertical pulverized coal boiler ammonia-coal coupling ultra-low nitrogen combustion system in any one of the above, and the combustion method includes: Controlling each layer of burners to introduce corresponding combustion gases and combustion-supporting air and simultaneously controlling the ignition of each layer of burners; By adjusting the delivery ratios of the primary combustion-supporting air, ammonia, secondary combustion-supporting air, and pulverized coal air of the lower burner, the temperature of the lower combustion zone 101 is maintained below 800 °C, and the air excess coefficient is maintained below 1; By adjusting the delivery ratios of the primary combustion-supporting air, ammonia, secondary combustion-supporting air, and pulverized coal air of the middle-layer burner, the temperature of the middle-layer combustion zone 102 is maintained at a temperature higher than 1000 °C, and the air excess coefficient is maintained between 1.1 and 1.3; By adjusting the delivery ratios of the combustion-supporting air and ammonia of the upper-layer pure ammonia burner 300, the temperature of the upper-layer combustion zone 103 is maintained slightly lower than the temperature of the middle-layer combustion zone 102, and the air excess coefficient is between 0.5 and 0.8.

[0038] The steps of maintaining the temperature of the lower-layer combustion zone 101 below 800 °C and maintaining the air excess coefficient below 1 by adjusting the delivery ratios of the primary combustion-supporting air, ammonia, secondary combustion-supporting air, and pulverized coal air of the lower-layer burner specifically include: Restrict the flow rate of the primary combustion-supporting air to enable lean-oxygen pre-combustion of ammonia in the ammonia combustion channel 205 and reduce the initial combustion intensity; By adjusting the valves or baffles of the secondary combustion-supporting air channel 204, reduce the total oxygen supply to ensure that the overall air excess coefficient λ < 1; After partial combustion of ammonia in the combustion channel, it is mixed with the pulverized coal in the pulverized coal air channel 203, and the environment with some oxygen consumed is used to suppress the subsequent combustion temperature. Temperature control and air excess coefficient control are jointly achieved through staged oxygen supply and staged fuel combustion.

[0039] Control the input ratio of ammonia and pulverized coal through a flow meter, use the high nitrogen content of ammonia to dilute the oxygen concentration in the combustion zone, and at the same time reduce the combustion heat release rate: Realize the premixed combustion of ammonia and the primary combustion-supporting air in the ammonia combustion channel 205, and then introduce pulverized coal into the mixed combustion channel to form a locally oxygen-deficient diffusion combustion environment.

[0040] In addition, due to the installation of temperature sensors, temperature monitoring and dynamic adjustment can be carried out. The temperature signal is fed back to the controller in real time through the temperature sensors, and the flow rates of ammonia, pulverized coal, or secondary combustion-supporting air are dynamically adjusted. The oxygen content in the flue gas is also monitored through oxygen concentration sensors, and the λ value is calculated in combination with the fuel input amount, and the supply amount of combustion-supporting air is automatically adjusted.

[0041] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. Vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system, characterized in that: include: The boiler body has an ash discharge port at the bottom and a smoke discharge port at the top. The boiler body has a lower combustion zone, a middle combustion zone and an upper combustion zone in sequence from bottom to top; The side walls and / or four corners of the lower combustion zone are provided with lower burners, the side walls and / or four corners of the middle combustion zone are provided with middle burners, and the side walls and / or four corners of the upper combustion zone are provided with upper burners. The lower burners and the middle burners are ammonia-coal co-firing burners, and the upper burners are pure ammonia burners. The ammonia-coal co-combustion burner is provided with an ammonia channel, a primary combustion-supporting air channel, a pulverized coal air channel, a secondary combustion-supporting air channel, an ammonia combustion channel, an ammonia-coal mixed combustion channel and a first ignition gun. The ammonia channel and the primary combustion-supporting air channel are both connected to the ammonia combustion channel. The first ignition gun is arranged in the ammonia combustion channel. The ammonia combustion channel, the pulverized coal air channel and the secondary combustion-supporting air channel are all connected to the ammonia-coal mixed combustion channel.

2. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 1 is characterized in that: The ammonia-coal co-firing burner includes a first shell, a second shell, a third shell, and a fourth shell. The third shell is sleeved in the fourth shell, the second shell is sleeved in the third shell, the first shell is sleeved in the second shell, the first ignition gun is arranged in the first shell, the ammonia channel is formed between the side wall of the first ignition gun and the first shell, the primary combustion-supporting air channel is formed between the first shell and the second shell, the ammonia combustion channel is formed in the second shell, the pulverized coal air channel is formed between the second shell and the third shell, the secondary combustion-supporting air channel is formed between the third shell and the fourth shell, and the ammonia-coal mixed combustion channel is formed in the fourth shell.

3. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 2 is characterized in that: The ammonia channel, the primary combustion-supporting air channel, the pulverized coal air channel, and the secondary combustion-supporting air channel are all annular channels.

4. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 3 is characterized in that: The first shell is provided with a plurality of first ammonia outlets for spraying ammonia in the radial direction of the first shell and a plurality of second ammonia outlets for spraying ammonia in the axial direction of the first shell at one end close to the ammonia combustion channel.

5. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 4 is characterized in that: The primary combustion-supporting air channel is provided with a swirl air outlet structure.

6. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 3 is characterized in that: The first ignition gun is located on the central axis of the first housing.

7. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 2 is characterized in that: A diffusion section is provided at one end of the second shell body close to the ammonia-coal mixed combustion channel, and the diameter of the diffusion section gradually increases along the spraying direction of the flame of the first ignition gun.

8. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 1 is characterized in that: The pure ammonia burner includes a fifth shell, a sixth shell and a second ignition gun. The fifth shell is sleeved in the sixth shell, and the second ignition gun is arranged in the fifth shell. An ammonia delivery channel is formed between the side wall of the second ignition gun and the fifth shell, and a combustion-supporting air channel is formed between the fifth shell and the sixth shell. The sixth shell is provided with a pure ammonia combustion channel, and the ammonia delivery channel and the combustion-supporting air channel are both connected to the pure ammonia combustion channel.

9. The vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to claim 8 is characterized in that: The second ignition gun is located on the central axis of the fifth housing.

10. A combustion method, characterized in that: It is applied to the vertical pulverized coal boiler ammonia-coal coupled ultra-low nitrogen combustion system according to any one of claims 1 to 9, and the combustion method comprises: Control the burners on each layer to introduce corresponding combustion gas and combustion-supporting air, and control the ignition of the burners on each layer; By adjusting the delivery ratio of primary combustion air, ammonia, secondary combustion air and pulverized coal air of the lower burner, the temperature of the lower combustion zone is kept below 800°C and the excess air coefficient is kept below 1; By adjusting the delivery ratio of primary combustion air, ammonia, secondary combustion air and pulverized coal air of the middle burner, the temperature of the middle combustion zone is kept above 1000℃ and the excess air coefficient is kept between 1.1 and 1.3; By adjusting the combustion-supporting air and ammonia delivery ratio of the upper pure ammonia burner, the temperature of the upper combustion zone is kept slightly lower than that of the middle combustion zone, and the excess air coefficient is between 0.5 and 0.8.

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