Low-nitrogen combustion device of medium-temperature separation circulating fluidized bed boiler
By designing a closed coal feeder, a coal supply and air prefluidization system and a heat-resistant guide baffle in the medium-temperature separation circulating fluidized bed boiler, the problems of high denitrification energy consumption and uneven distribution of nitrogen oxides during the combustion process of the medium-temperature separation circulating fluidized bed boiler were solved, and a high-efficiency and low-nitrogen oxide emission combustion effect was achieved.
Patent Information
- Application Number
- CN202510972104.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-15
- Publication Date
- 2025-09-19
AI Technical Summary
The medium-temperature separation circulating fluidized bed boiler has problems such as high denitrification energy consumption, uneven distribution of nitrogen oxides, high ammonia escape and low combustion efficiency during the combustion process, especially the oxygen-enriched combustion produces a large amount of nitrogen oxides during operation.
A medium-temperature separation circulating fluidized bed boiler low-nitrogen combustion device is adopted. By evenly distributing water-cooled wall pipes on the water-cooled wall of the boiler front wall, combined with a closed coal feeder, a coal supply and air pre-fluidization system, a heat-resistant guide baffle and a multi-chamber self-locking wind hood and other designs, uniform coal powder injection and uniform air-coal mixing are achieved, high-temperature flue gas backflow is avoided, and the combustion process is optimized.
It achieves uniform combustion of pulverized coal in the furnace, reduces nitrogen oxide emissions, improves combustion efficiency, improves combustion efficiency and combustion efficiency, and reduces energy consumption.
Smart Images
Figure CN120667716A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of boiler combustion, and in particular to a low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler. Background Art
[0002] During combustion in a circulating fluidized bed boiler, a high-speed airflow (primary air) flows upward from the boiler's bottom air distribution plate through the particle bed, causing the bed material (fuel, limestone, slag, etc.) to transition from a static state to a fluid-like state of motion, a process known as fluidization. The particles then churn and mix vigorously within the airflow, forming a "fluidized bed" that allows for thorough contact and mixing between the fuel and air, creating conditions for efficient combustion. However, current medium-temperature separation fluidized bed boilers often utilize flue gas recirculation and combined SCR and SNCR denitrification technologies to meet NOx emission standards. However, this denitrification process consumes a lot of energy and results in uneven distribution of nitrogen oxides and high ammonia slip. Furthermore, current medium-temperature separation circulating fluidized bed boilers mostly operate with rear-wall coal feeding and direct injection of secondary and tertiary air, resulting in low combustion efficiency and the generation of large amounts of nitrogen oxides through oxygen-enriched combustion. Consequently, the present invention proposes a low-nitrogen combustion device for medium-temperature separation circulating fluidized bed boilers. Summary of the Invention
[0003] The purpose of the present invention is to provide a low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler to solve the above-mentioned problems.
[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0005] The present invention provides a low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler, comprising a boiler, wherein a plurality of water-cooled wall pipe outlets are evenly distributed on the water-cooled wall of the front wall of the boiler, the water-cooled wall pipe outlets are connected to an inclined coal drop pipe through a flange, the other end of the coal drop pipe is connected to a closed coal feeder discharge port on the outer side wall, and the other end of the closed coal feeder discharge port is connected to a horizontally arranged closed coal feeder; a primary air duct is provided at the bottom of the boiler, and a coal supply air distribution prefluidization system is provided between the primary air duct, the coal drop pipe and the closed coal feeder; the combustion chamber of the boiler is connected to the secondary and tertiary air distribution systems.
[0006] Furthermore, a stainless steel coal dropping pipe expansion joint is vertically provided at the bottom of the discharge port of the closed coal feeder, and the stainless steel coal dropping pipe expansion joint is connected to the coal dropping pipe.
[0007] Furthermore, the coal feeding and air distribution prefluidization system includes a booster air interface provided on the outer side wall of the upper portion of the coal dropping pipe, the air outlet of the booster air interface being relatively distributed with the coal dropping pipe and being connected to the discharge port of the closed coal feeder; the booster air interface is connected to the primary cooling air duct through the booster air duct, the primary cooling air duct is connected to the front end of the primary air duct, and the front end of the primary air duct is located at the front end position of the primary air duct;
[0008] The primary cooling air duct is also connected to the sealed air duct, and the other end of the sealed air duct is connected to the sealed air interface on the closed coal feeder;
[0009] The front end of the primary air duct is also connected to an air preheater, the other end of the air preheater is connected to a coal-spreading air duct, the other end of the coal-spreading air duct is connected to a coal-spreading air duct interface at the lower part of the coal drop pipe, a coal drop pipe nozzle is provided at the bottom of the coal drop pipe, and the air outlet position of the coal-spreading air duct interface is distributed relative to the coal drop pipe nozzle.
[0010] Furthermore, the secondary and tertiary air distribution systems include secondary air ducts and nozzles and tertiary air ducts and nozzles symmetrically arranged on the outer wall of the boiler, the secondary air ducts and nozzles and the tertiary air ducts and nozzles are symmetrically distributed up and down, and the secondary air ducts and nozzles and the tertiary air ducts and nozzles are all connected to the secondary air duct;
[0011] The secondary air duct is also connected to the prefluidized air duct, and the other end of the prefluidized air duct is connected to the prefluidized air interface on the top of the coal dropping pipe. The air outlet direction of the prefluidized air interface is parallel to the coal dropping direction of the coal dropping pipe.
[0012] Furthermore, the nozzle cross-sections of the secondary air duct and nozzle and the tertiary air duct and nozzle are both provided with heat-resistant guide baffles, and the installation angle between the heat-resistant guide baffles and the secondary air duct and nozzle / tertiary air duct and nozzle is 60°.
[0013] Furthermore, non-metallic compensators are respectively provided on the secondary air duct and nozzle and the tertiary air duct and nozzle.
[0014] Furthermore, the secondary air duct and the nozzle are provided with a secondary air regulating door, and the tertiary air duct and the nozzle are provided with a tertiary air electric regulating door.
[0015] Furthermore, a plurality of multi-chamber self-locking hoods are evenly spaced at the bottom of the boiler, and a slag discharge pipe is provided in the middle of the bottom of the boiler.
[0016] Compared with the prior art, the present invention has the following beneficial technical effects:
[0017] 1. The design of the coal-feeding air pre-fluidization system avoids the problem of uneven mixing of air and bed material and low combustion efficiency, prevents the high-temperature flue gas in the furnace from flowing back to the coal feeder, and can also adjust the air supply volume according to the coal feed amount, so that the air flow is dispersed and the air-coal mixing is more uniform;
[0018] 2. Install heat-resistant guide baffles on the secondary and tertiary air nozzles to improve the unstable air inlet, low wind speed, and insufficient fluidization in the furnace, and avoid the problem of local oxygen-enriched combustion caused by excessive air supply in some areas;
[0019] 3. The multi-chamber self-locking hood solves the problem of uneven air supply caused by excessive local resistance of the bed material.
[0020] In summary, the low-nitrogen combustion device of the medium-temperature separation circulating fluidized bed boiler of the present invention sprays pulverized coal evenly into the main combustion zone of the furnace, and completes the auxiliary fuel drying and pre-fluidization before entering the furnace, thereby avoiding uneven air distribution in the main combustion zone and overheating and coking of local heating surfaces, while saving the fluidizing air volume in the main combustion zone, ensuring sufficient oxygen and complete combustion of fuel when the boiler is running at high load, and reducing nitrogen oxide emissions. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be further described below with reference to the accompanying drawings.
[0022] Figure 1 This is a cross-sectional view of a low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to the present invention;
[0023] Figure 2 Installation diagram of the coal drop pipe;
[0024] Figure 3 This is a diagram of the distribution structure of the multi-chamber self-locking hood;
[0025] Figure 4 This is the secondary and tertiary air duct system diagram;
[0026] Figure 5 This is a diagram of the coal-to-air distribution system;
[0027] Figure 6 This is the air duct layout diagram of the closed coal feeder;
[0028] Figure 7 This is a structural diagram of the guide baffle in the installed state;
[0029] Description of reference numerals:
[0030] 1. Enclosed coal feeder; 2. Enclosed coal feeder discharge port; 3. Stainless steel coal drop pipe expansion joint; 4. Coal drop pipe; 5. Coal drop pipe nozzle; 6. Water wall pipe outlet; 7. Prefluidizing air interface; 8. Coal spreading air duct interface; 9. Power assist air interface; 10. Sealing air interface; 11. Front wall water wall; 12. Secondary air duct and nozzle; 13. Rear wall water wall; 14. Multi-chamber self-locking hood; 15. Primary air duct; 16. Side wall Water-cooled wall; 17. Flange; 18. Slag discharge pipe; 19. Secondary air regulating door; 20. Non-metallic compensator; 21. Tertiary air duct and nozzle; 22. Tertiary air electric regulating door; 23. Power-assisted air duct; 24. Sealed air duct; 25. Prefluidizing air duct; 26. Secondary air duct; 27. Primary cooling air duct; 28. Front end of primary air duct; 29. Air preheater; 30. Coal-spreading air duct; 31. Heat-resistant guide baffle. DETAILED DESCRIPTION
[0031] like Figure 1-7 As shown, a medium-temperature separation circulating fluidized bed boiler low-nitrogen combustion device includes a boiler, and the boiler includes a front wall water-cooled wall 11 and a rear wall water-cooled wall 13. The front wall water-cooled wall 11 and the rear wall water-cooled wall 13 are connected together by a side wall water-cooled wall 16. There are a number of water-cooled wall pipe outlets 6 evenly distributed on the front wall water-cooled wall 11. The water-cooled wall pipe outlets 6 are connected to the inclined coal drop pipe 4 through a flange 17. The gap is sealed with refractory castables to isolate the furnace and reduce heat loss. The angle between the coal drop pipe 4 and the horizontal direction of the water-cooled wall is 55 degrees. This angle is more conducive to the coal falling into the furnace and reduces coal accumulation. The other end of the coal drop pipe 4 is connected to the outer wall of the closed coal feeder discharge port 2, and the other end of the closed coal feeder discharge port 2 is connected to the horizontally installed closed coal feeder 1. A stainless steel coal drop pipe expansion joint 3 is vertically installed at the bottom of the closed coal feeder discharge port 2. The stainless steel coal drop pipe expansion joint 3 is connected to the coal drop pipe 4. The stainless steel coal drop pipe expansion joint 3 can effectively reduce the impact of falling coal on the coal drop pipe and isolate the influence of the vibration of the closed coal feeder 1 on the furnace.
[0032] Specifically, four closed coal feeders 1 are used in this embodiment. The use of a fully sealed coal feeder can reduce air leakage in the coal feeding system. At the same time, the four coal feeders feed coal more evenly. When a single coal feeder fails, the coal flow of other coal feeders can be increased, which can further reduce the disturbance to boiler combustion and nitrogen oxide adjustment.
[0033] A primary air duct 15 is installed at the bottom of the boiler, and a coal air distribution and pre-fluidization system is installed between the primary air duct 15, the coal drop pipe 4 and the closed coal feeder 1; the combustion chamber of the boiler is connected to the secondary and tertiary air distribution systems.
[0034] The coal feeding and air distribution prefluidization system includes a boosting air interface 9 installed on the upper outer wall of the coal dropping pipe 4, and the air outlet of the boosting air interface 9 is relatively distributed with the coal dropping pipe 4 and connected to the discharge port of the closed coal feeder 2; the boosting air interface 9 is connected to the primary cold air duct 27 through the boosting air duct 23, and the primary cold air duct 27 is connected to the front end 28 of the primary air duct, and the front end 28 of the primary air duct is located at the front end position of the primary air duct 15; the boosting air duct 23 is provided with an electric regulating door and a pressure gauge for accurately adjusting the air intake volume. After the air enters the coal dropping pipe 4, a layer of air cushion is formed on the inner wall of the coal dropping pipe 4 to prevent the coal dropping pipe 4 from being blocked, and at the same time supplement the oxygen required for combustion.
[0035] The primary cold air duct 27 is also connected to the sealed air duct 24, and the other end of the sealed air duct 24 is connected to the sealed air interface 10 on the closed coal feeder 1; the sealed air duct 24 is provided with an electric regulating door and a pressure gauge to ensure that the sealed air pressure is greater than the pressure in the furnace, thereby preventing the high-temperature flue gas in the furnace from flowing back to the closed coal feeder 1.
[0036] In this embodiment, when the coal entering the furnace has a small particle size and a high volatile content, the coal spreading air or primary fan current is reduced to achieve nitrogen oxide control. When the coal entering the furnace has an increased particle size and a decreased volatile content, the primary fan current needs to be appropriately increased to ensure sufficient fluidized combustion, thereby improving combustion economy while ensuring that nitrogen oxide levels are within acceptable limits. Specifically, when the load is 200-220T / H and the coal feed rate is 37-40T / H, the primary fan current is maintained at 46A-48A; when the load is 180-200T / H and the coal feed rate is 33-36T / H, the primary fan current is maintained at 43A-45A; when the load is 180T / H and the coal feed rate is below 32T / H, the primary fan current is maintained at 39A-42A; this allows the main combustion zone to undergo appropriate oxygen-deficient combustion to reduce nitrogen oxide generation.
[0037] The front end 28 of the primary air duct is also connected to an air preheater 29. The other end of the air preheater 29 is connected to a coal-spreading air duct 30. The other end of the coal-spreading air duct 30 is connected to a coal-spreading air duct interface 8 at the bottom of the coal drop pipe 4. A coal drop pipe nozzle 5 is installed at the bottom of the coal drop pipe 4, and the air outlet of the coal-spreading air duct interface 8 is located opposite the coal drop pipe nozzle 5. The primary air is heated to 130 degrees Celsius by the air preheater 29 and becomes coal-spreading air. It then enters the furnace through the coal-spreading air duct interface 8. An electrically adjustable door and pressure gauge are located at the front end of the coal-spreading air duct interface 8. During operation, the coal-spreading air volume is adjusted to disperse the raw coal into the furnace, mixing it more evenly with the bed material and ensuring more complete combustion.
[0038] The secondary air duct 26 is also connected to the prefluidized air duct 25. The other end of the prefluidized air duct 25 is connected to the prefluidized air interface 7 at the top of the coal drop pipe 4. The air outlet direction of the prefluidized air interface 7 is parallel to the coal drop direction of the coal drop pipe 4. Since the secondary air temperature reaches 170°C, it has the functions of preheating and drying the raw coal, mixing and fluidizing it, and boosting the fuel. It can be preheated before the raw coal enters the furnace for combustion, and at the same time replenish the oxygen required for high-load operation. An electric regulating door and pressure gauge are set at the front end of the prefluidized air interface 7. During operation, the prefluidized air volume and pressure are adjusted according to the coal feed and boiler load to avoid the generation of large amounts of nitrogen oxides due to turning on the primary fan and coal spreading air.
[0039] By adopting the above-mentioned technical solution of the coal supply and air prefluidization system and the secondary air prefluidization method, the coal powder is evenly sprayed into the main combustion zone of the furnace, and the auxiliary fuel is dried and prefluidized before entering the furnace, thereby avoiding uneven air distribution in the main combustion zone and overheating and coking of local heating surfaces. At the same time, the fluidizing air volume in the main combustion zone is saved, which can ensure sufficient oxygen and complete combustion of fuel when the boiler is running at high load and reduce nitrogen oxide emissions.
[0040] The secondary and tertiary air distribution systems include a secondary air duct and nozzle 12 and a tertiary air duct and nozzle 21 symmetrically mounted on the outer wall of the boiler. The secondary air duct and nozzle 12 and the tertiary air duct and nozzle 21 are symmetrically distributed up and down, and are both connected to the secondary air duct 26. The secondary air duct and nozzle 12 and the tertiary air duct and nozzle 21 both adopt waisted ducts on both sides. A secondary air regulating door 19 is installed on the secondary air duct and nozzle 12, and a tertiary air electric regulating door 22 is installed on the tertiary air duct and nozzle 21. Several multi-chamber self-locking air hoods 14 are evenly spaced at the bottom of the boiler, and a slag lowering pipe 18 is installed in the middle of the bottom of the boiler. That is, the secondary and tertiary air systems are controlled separately, realizing separate control and adjustment of the secondary and tertiary air volumes to ensure a more uniform mixing of air and coal.
[0041] Heat-resistant guide baffles 31 are installed on the nozzle cross-sections of the secondary air duct and nozzle 12 and the tertiary air duct and nozzle 21. The heat-resistant guide baffles 31 are installed at a 60° angle to the secondary air duct and nozzle 12 / tertiary air duct and nozzle 21. The heat-resistant guide baffles 31 prevent nozzle deformation and ensure more uniform air supply. Non-metallic compensators 20 are installed on the secondary air duct and nozzle 12 and the tertiary air duct and nozzle 21 respectively.
[0042] By adopting the above-mentioned secondary and tertiary air distribution system technical solutions, the waisted air inlet can increase the wind speed and pressure, increase the disturbance area and effect of the air flow in the furnace, and avoid the production of large amounts of nitrogen oxides due to local oxygen enrichment.
[0043] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.
Claims
1. A medium-temperature separation circulating fluidized bed boiler low-nitrogen combustion device, characterized by: The invention comprises a boiler, wherein a plurality of water-cooled wall pipe outlets (6) are evenly distributed on the front water-cooled wall (11) of the boiler, the water-cooled wall pipe outlets (6) are connected to an inclined coal drop pipe (4) through a flange (17), the other end of the coal drop pipe (4) is connected to a closed coal feeder discharge port (2) on the outer wall, and the other end of the closed coal feeder discharge port (2) is connected to a horizontally arranged closed coal feeder (1); a primary air duct (15) is provided at the bottom of the boiler, and a coal supply air pre-fluidization system is provided between the primary air duct (15), the coal drop pipe (4) and the closed coal feeder (1); and the combustion chamber of the boiler is connected to the secondary and tertiary air supply systems.
2. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 1, characterized in that: A stainless steel coal drop pipe expansion joint (3) is vertically provided at the bottom of the closed coal feeder discharge port (2), and the stainless steel coal drop pipe expansion joint (3) is in communication with the coal drop pipe (4).
3. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 1, characterized in that: The coal feeding and air distribution prefluidization system includes a boosting air interface (9) provided on the outer side wall of the upper portion of the coal dropping pipe (4), the air outlet of the boosting air interface (9) being relatively distributed with the outlet of the coal dropping pipe (4) and connected to the discharge port of the closed coal feeder (2); the boosting air interface (9) is connected to the primary cold air duct (27) through the boosting air duct (23), the primary cold air duct (27) is connected to the front end (28) of the primary air duct, and the front end (28) of the primary air duct is located at the front end of the primary air duct (15); The primary cold air duct (27) is also connected to the sealed air duct (24), and the other end of the sealed air duct (24) is connected to the sealed air interface (10) on the closed coal feeder (1); The front end (28) of the primary air duct is also connected to an air preheater (29), the other end of the air preheater (29) is connected to a coal spreading air duct (30), the other end of the coal spreading air duct (30) is connected to a coal spreading air duct interface (8) at the lower part of the coal dropping pipe (4), a coal dropping pipe nozzle (5) is provided at the bottom of the coal dropping pipe (4), and the air outlet position of the coal spreading air duct interface (8) is distributed relative to the coal dropping pipe nozzle (5).
4. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 1, characterized in that: The secondary and tertiary air distribution systems include a secondary air duct and nozzle (12) and a tertiary air duct and nozzle (21) symmetrically arranged on the outer wall of the boiler, wherein the secondary air duct and nozzle (12) and the tertiary air duct and nozzle (21) are symmetrically distributed up and down, and the secondary air duct and nozzle (12) and the tertiary air duct and nozzle (21) are both connected to the secondary air duct (26); The secondary air duct (26) is also connected to the prefluidized air duct (25), and the other end of the prefluidized air duct (25) is connected to the prefluidized air interface (7) at the top of the coal dropping pipe (4), and the air outlet direction of the prefluidized air interface (7) is parallel to the coal dropping direction of the coal dropping pipe (4).
5. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 4, characterized in that: The nozzle cross-sections of the secondary air duct and nozzle (12) and the tertiary air duct and nozzle (21) are both provided with heat-resistant flow guide baffles (31), and the installation angle between the heat-resistant flow guide baffles (31) and the secondary air duct and nozzle (12) / tertiary air duct and nozzle (21) is 60°.
6. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 4, characterized in that: The secondary air duct and nozzle (12) and the tertiary air duct and nozzle (21) are respectively provided with non-metallic compensators (20).
7. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 4, characterized in that: The secondary air duct and the nozzle (12) are provided with a secondary air regulating door (19), and the tertiary air duct and the nozzle (21) are provided with a tertiary air electric regulating door (22).
8. The low-nitrogen combustion device for a medium-temperature separation circulating fluidized bed boiler according to claim 1, characterized in that: A plurality of multi-chamber self-locking hoods (14) are arranged at equal intervals on the bottom of the boiler, and a slag discharge pipe (18) is provided in the middle of the bottom of the boiler.