A circulating fluidized bed boiler air distribution plate dust retaining and flow stabilizing structure

Abstract

The present application relates to the technical field of air distribution plate of circulating fluidized bed boiler, and proposes a kind of air distribution plate of circulating fluidized bed boiler dust retaining stable flow structure, including air distribution plate, air distribution plate is equipped with multiple air caps, air distribution plate top is equipped with multiple dust retaining plates at intervals, each dust retaining plate is parallel to each other, and the fluidized bed zone between each adjacent two dust retaining plates;Air cap is distributed in the interplate fluidized zone, and the height of dust retaining plate is greater than the height of air cap.The present application is adopted, by setting dust retaining plate in air distribution plate to divide independent fluidization area, block large-scale transverse channeling of bottom bed material, weaken the flow field disturbance caused by uneven coal feeding, return material etc., effectively inhibit the large amplitude periodic fluctuation of bed pressure on left and right sides of air distribution plate, while reducing the scouring and wearing of bed material to air cap, improve the reliability of boiler operation.

Description

Technical Field

[0001] This invention relates to the field of air distribution plate technology for circulating fluidized bed boilers, and more specifically, to an ash-blocking and flow-stabilizing structure for air distribution plates in circulating fluidized bed boilers. Background Technology

[0002] Circulating fluidized bed combustion technology boasts advantages such as wide fuel adaptability and low pollutant emissions, and has been widely applied in large-scale coal-fired power plants and industrial heating. As units continue to develop towards larger sizes and higher parameters, the overall furnace size continues to increase, and the width-to-depth ratio of the air distribution plate at the bottom of the furnace is gradually improving. Currently, the width-to-depth ratio of the air distribution plate in mainstream units has reached 10:1, and there is still a trend of further increase. To improve the economic efficiency of unit operation, fine-particle coal is commonly used on-site, paired with a high-efficiency cyclone separator, resulting in a finer overall particle size of the circulating bed material in the furnace; fine-particle bed material has lower flow resistance and stronger fluidity.

[0003] During normal boiler operation, the bed material above the air distributor plate is fluidized under the action of primary air, maintaining a dynamic equilibrium. A large aspect ratio air distributor plate and fine-grained bed material are the two fundamental conditions inducing abnormal bed pressure fluctuations. Uneven distribution of coal feed, return material, and internal material circulation during operation becomes the main triggering factor for disrupting the fluidization equilibrium. After imbalance, the bed material forms a wave-like overall surge, ultimately manifesting as large-amplitude, regular, periodic fluctuations in bed pressure on both sides of the air distributor plate. This problem has been widely observed in many large-scale boiler projects, seriously affecting stable boiler operation.

[0004] Fluctuations in bed pressure can directly cause disorder in the fluidized bed conditions inside the furnace, leading to problems such as uneven combustion, steam temperature deviation, local coking, limited load regulation, and boiler shutdown due to bed turnover, which seriously reduces the stability and reliability of boiler operation.

[0005] Existing optimization solutions for bed pressure fluctuations mainly fall into three categories: first, optimizing the air chamber structure and adjusting the primary air volume in different zones; second, modifying the air cap structure to adjust local air distribution resistance; and third, adding flow guiding and obstruction components in the furnace water-cooled wall area. None of these existing technologies can fundamentally solve the problem: air volume adjustment is limited by unit load and the type of coal fed into the furnace, making it difficult to offset large-scale bed material disturbances; the furnace flow guiding components are positioned too high, only able to regulate the flow along the upper wall of the furnace, with limited effect on dense-phase bed materials in the air distribution plate area; and air cap modifications only optimize the air supply effect and cannot suppress lateral bed material flow. Summary of the Invention

[0006] The purpose of this invention is to provide an ash-blocking and flow-stabilizing structure for the air distribution plate of a circulating fluidized bed boiler. By setting ash-blocking plates on the air distribution plate to divide the independent fluidization zone, the large-scale lateral flow of the bottom bed material is blocked, the flow field disturbance caused by uneven coal feeding and return is weakened, the large-scale periodic fluctuation of bed pressure on the left and right sides of the air distribution plate is effectively suppressed, and the scouring and wear of the bed material on the air cap is reduced, thereby improving the reliability of boiler operation.

[0007] The technical solution adopted in this invention is as follows: This application provides a circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure, including an air distribution plate, the air distribution plate is provided with a plurality of air caps, and a plurality of ash-blocking plates are spaced apart on the top of the air distribution plate. The ash-blocking plates are parallel to each other, and the space between each two adjacent ash-blocking plates is a fluidization zone between the plates. The air caps are distributed in the fluidization zone between the plates, and the height of the ash-blocking plates is greater than the height of the air caps.

[0008] Furthermore, in this invention, the plane where the dust baffle is located is perpendicular to the plane where the air distribution plate is located.

[0009] Furthermore, in this invention, the dust baffle is inclined on the air distribution plate, and the included angle α between the dust baffle and the air distribution plate is in the range of 60°≤a<90°.

[0010] Furthermore, in this invention, the maximum height between the top of the dust baffle and the top of the air distribution plate is 300-800 mm.

[0011] Furthermore, in this invention, the thickness of the dust baffle is 50mm to 300mm.

[0012] Furthermore, in this invention, the spacing between two adjacent dust baffles is 2m to 10m.

[0013] Furthermore, in this invention, the top of the dust baffle is provided with an arc-shaped chamfer.

[0014] Furthermore, in this invention, the tops of each dust baffle are kept flush.

[0015] Furthermore, in this invention, the dust baffles are arranged at uniform intervals along the width direction of the air distribution plate.

[0016] Compared with the prior art, the present invention has at least the following advantages or beneficial effects: This application provides a circulating fluidized bed boiler air distributor plate ash-blocking and flow-stabilizing structure. The ash-blocking plate divides the high aspect ratio air distributor plate into multiple small fluidization zones, blocking large-scale lateral flow and wave-like surging of bed material, greatly reducing bed pressure fluctuations and completely improving the problem of periodic bed pressure fluctuations on both sides of the air distributor plate. The zoned structure weakens the flow field disturbances caused by uneven distribution of coal and return material, making the fluidization state, temperature field, and material circulation in the furnace more uniform and stable, effectively avoiding faults such as local coking and poor ash discharge. The vertical ash-blocking plate blocks high-speed... The bed material directly washes against the air cap, significantly reducing the wear rate of the air cap, extending the service life of the equipment, and reducing the unit's operation and maintenance costs and workload. This structure does not require modification of the original air chamber, air duct, and air cap system. New boilers can be directly integrated into the design, and existing units can be retrofitted on-site. The construction process is simple, the retrofit cost is low, and the construction period is short. The ash baffle plate arrangement is flexible. The arrangement and structural parameters can be adjusted according to the size of the air distribution plate, the width-to-depth ratio, the ash discharge position, and the unit capacity, making it suitable for large circulating fluidized bed boilers of different specifications and highly versatile. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a front view of the ash-blocking and flow-stabilizing structure of the air distribution plate of the circulating fluidized bed boiler provided in Embodiment 1 of the present invention; Figure 2 This is a top view of the ash-blocking and flow-stabilizing structure of the air distribution plate of the circulating fluidized bed boiler provided in Embodiment 1 of the present invention; Figure 3 This is a front view of the ash-blocking and flow-stabilizing structure of the air distribution plate of the circulating fluidized bed boiler provided in Embodiment 2 of the present invention; Figure 4 This is a front view of the ash-blocking and flow-stabilizing structure of the air distribution plate of the circulating fluidized bed boiler provided in Embodiment 3 of the present invention.

[0019] Icons: 1-Air distribution plate; 2-Air cap; 3-Dust baffle; 31-Fluidized zone between plates; 32-Curved chamfer; 4-Furnace chamber; 5-Air chamber. Detailed Implementation

[0020] The embodiments of this application will now be described in detail with reference to the accompanying drawings. Example

[0021] Existing large-scale generating units have a large width-to-depth ratio of air distributor plates, and the bed material in the furnace is relatively fine and highly fluid, which are inherent conditions for bed pressure fluctuations. During operation, uneven distribution of coal feeding, return material, and internal material circulation easily triggers fluidization imbalance, causing large-amplitude, regular, and periodic fluctuations in bed pressure on both sides of the air distributor plate. Existing conventional methods such as airflow regulation, furnace diversion, and air cap modification cannot completely stop the overall surging and lateral flow of the bed material, resulting in poor suppression of bed pressure fluctuations and severely restricting the unit's load regulation and safe, stable operation. Therefore, please refer to... Figures 1-2 This embodiment provides a circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure. This structure is suitable for large circulating fluidized bed boilers with an air distribution plate width-to-depth ratio of not less than 5:1. It includes an air distribution plate 1, which is installed above the air chamber 5. The air distribution plate 1 is provided with a plurality of air caps 2, which are evenly arranged in an array on the surface of the air distribution plate 1, connecting the lower air chamber 5 and the dense phase zone of the upper furnace 4. A plurality of ash-blocking plates 3 are spaced apart on the top of the air distribution plate 1. The ash-blocking plates 3 are parallel to each other, and the space between each two adjacent ash-blocking plates 3 is an inter-plate fluidization zone 31. The air caps 2 are distributed in the inter-plate fluidization zone 31, and the height of the ash-blocking plates 3 is greater than the height of the air caps 2. The large-sized air distribution plate 1 is divided into several independent inter-plate fluidization zones 31 by the multiple spaced ash-blocking plates 3. The ash-blocking plates 3 effectively block the lateral flow of the bed material in the lower area, while allowing the bed material in the upper area of ​​the ash-blocking plates 3 to flow and mix laterally. The ash baffle 3 can be a one-piece structure or a segmented splicing structure. For example, multiple small ash baffles 3 can be spliced ​​together to form a whole, which can be fixed with bolts or spliced ​​with mortise and tenon joints. Preferably, the tops of each ash baffle 3 are flush, and the ash baffles 3 are evenly spaced along the width of the air distribution plate 1. The plane of the ash baffle 3 is perpendicular to the plane of the air distribution plate 1. In this embodiment, the ash baffle 3 is made of wear-resistant metal sheet or wear-resistant refractory castable, and is connected to the air distribution plate 1 by welding, bolt fixing, or integral casting.

[0022] Therefore, this application provides a circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure. The ash-blocking plate 3 divides the air distribution plate 1 with a large aspect ratio into multiple small fluidization zones (inter-plate fluidization zones 31), blocking the large-scale lateral flow and wave-like surging of bed material, greatly reducing the bed pressure fluctuation amplitude, and completely improving the problem of periodic bed pressure fluctuation on the left and right sides of the air distribution plate; the zoned structure weakens the flow field disturbance caused by uneven distribution of coal and return material, making the fluidization state, temperature field, and material circulation in the furnace more uniform and stable, effectively avoiding faults such as local coking and poor slag discharge; vertical ash-blocking plate 3. The high-speed bed material directly erodes the air cap 2, significantly reducing the wear rate of the air cap 2, extending the service life of the equipment, and reducing the unit's operation and maintenance costs and workload. This structure does not require modification of the original air chamber, air duct, and air cap system. New boilers can be directly integrated into the design, and in-service units can be retrofitted on-site. The construction process is simple, the modification cost is low, and the construction period is short. The ash baffle plate 3 has a flexible arrangement. The arrangement and structural parameters can be adjusted according to the size of the air distribution plate 1, the width-to-depth ratio, the ash discharge position, and the unit capacity. It is suitable for large circulating fluidized bed boilers of different specifications and has strong versatility.

[0023] like Figures 1-2 As shown, in some embodiments, the maximum height between the top of the baffle plate 3 and the top of the air distribution plate 1 is 300-800 mm. Since the air cap 2 itself can play a certain role in blocking dust, the newly added baffle plate 3 does not need to be as high as or lower than the air cap 2. Moreover, since the normal operating pressure of the fluidized bed is usually 4-8 kPa, the equivalent bed material thickness is approximately 400-800 mm. The height between the top of the air cap and the top of the air distribution plate 1 is usually 100-200 mm. Therefore, designing the maximum height between the top of the baffle plate 3 and the top of the air distribution plate 1 to be 300-800 mm is both greater than the height between the top of the air cap and the top of the air distribution plate 1 and can effectively block the bed material.

[0024] like Figures 1-2 As shown, in some embodiments, the thickness of the dust baffle 3 is 50mm to 300mm. In this application, the thickness of the dust baffle 3 is mainly designed according to its structure and needs to have stability and reliability. For example, if internal water cooling and external casting material are used, the thickness of the dust baffle 3 can be designed to be 150mm to 200mm. If better wear resistance is considered, the thickness of the dust baffle 3 can be designed to be 300mm.

[0025] like Figures 1-2As shown, in some embodiments, the spacing between two adjacent baffle plates 3 is 2m to 10m. Based on practical experience, the probability of bed pressure fluctuation is lower or even non-existent in smaller furnace types, for example, it rarely occurs in 135MW CFB boilers, but the probability increases in larger furnace types. Therefore, using the width of a 135MW furnace type as a design reference for the baffle plate spacing, the spacing between two adjacent baffle plates 3 is designed to be 2m to 10m, which can achieve a good baffle effect. Example

[0026] like Figure 3 As shown, the difference between this embodiment and Embodiment 1 is that in this embodiment, the ash baffle 3 is inclinedly arranged on the air distribution plate 1, and the included angle α between the ash baffle 3 and the air distribution plate 1 is in the range of 60°≤a<90°. The ash baffle 3 is preferably vertically arranged, but it can also be inclined. If the angle of inclination of the ash baffle 3 relative to the vertical plane is too large, it will cause its center of gravity to be too low, reducing its structural strength. This may cause the ash baffle 3 to tip over when the gas flows in the furnace. Therefore, the included angle α between the ash baffle 3 and the air distribution plate 1 is designed to be in the range of 60°≤a<90°, which ensures that the ash baffle 3 has strong structural strength and can achieve a good ash-blocking effect. Example

[0027] like Figure 4 As shown, the difference between this embodiment and Embodiment 1 is that the top of the dust baffle 3 in this embodiment is provided with an arc-shaped chamfer 32. The design of the arc-shaped chamfer 32 can reduce the erosion and wear on the top of the dust baffle 3 and improve the service life of the dust baffle 3.

[0028] A typical implementation method is as follows: Detailed Implementation Method 1

[0029] This embodiment is applied to a 660MW ultra-supercritical large-scale circulating fluidized bed boiler. The width-to-depth ratio of the air distribution plate is greater than 10:1. The ash baffle plate 3 is arranged vertically along the width direction of the air distribution plate 1. It adopts a segmented splicing structure with seamless connection between the segments and the top of the whole is kept flush.

[0030] The ash baffle plate 3 is integrally cast using wear-resistant and refractory castable and is integrated with the air distribution plate 1. The maximum distance between the top of the ash baffle plate 3 and the top of the air distribution plate 1 is 2.5 times the maximum distance between the top of the air cap 2 and the top of the air distribution plate 1. The thickness of the ash baffle plate 3 is 120mm, and the vertical distance between two adjacent ash baffle plates 3 is 10m. This structure can effectively block the large-scale lateral flow of fine particle bed material at the bottom, is suitable for ultra-large cross-section air distribution plate conditions, completely suppresses the periodic fluctuation of bed pressure on the left and right sides, and also has excellent wear resistance. Detailed Implementation Method 2

[0031] This embodiment is applicable to medium-sized and large-sized circulating fluidized bed boilers with a width-to-depth ratio of 5:1 for the air distribution plate. The ash baffles 3 are uniformly arranged vertically along the width of the air distribution plate 1, forming an integrated structure and installed vertically. The maximum distance between the top of the ash baffle 3 and the top of the air distribution plate 1 is twice the maximum distance between the top of the air cap 2 and the top of the air distribution plate 1. The thickness of the ash baffle 3 is 50mm, and the vertical distance between two adjacent ash baffles 3 is 5m. This arrangement, while ensuring normal fluidized mixing, effectively prevents large-scale lateral flow of fine-particle bed material at the bottom, effectively solving the problem of periodic fluctuations in bed pressure. It features a simple structure and good economic efficiency. Detailed Implementation Method 3

[0032] This embodiment is a retrofit project for an in-service large-scale circulating fluidized bed boiler. The original air distribution plate 1 and the entire structure of the air chamber are retained, and only part of the air cap 2 in the area of ​​the ash baffle plate 3 needs to be removed. The ash baffle plate 3 is arranged vertically along the width of the air distribution plate 1 and adopts a detachable structure, which is fixed to the pre-set mounting base of the air distribution plate by bolts or welding.

[0033] The thickness of the ash baffle plate 3 is 100mm. The maximum distance between the top of the ash baffle plate 3 and the top of the air distribution plate 1 is 1.8 times the maximum distance between the top of the air cap 2 and the top of the air distribution plate 1. The vertical distance between two adjacent ash baffle plates 3 is 8m, which is combined with the actual distribution of the coal feed port, return port, and slag discharge port on site. After the modification, the large-scale lateral flow of fine particle bed material at the bottom is effectively reduced, the bed pressure operation is stable, the modification construction is simple, and it does not affect the original structure and normal operation of the boiler.

Claims

1. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure, comprising an air distribution plate (1), wherein the air distribution plate (1) is provided with a plurality of air caps (2), characterized in that, The top of the air distribution plate (1) is provided with a plurality of dust baffles (3) spaced apart. Each dust baffle (3) is parallel to each other, and there is a fluidization zone (31) between each two adjacent dust baffles (3). The air cap (2) is distributed in the fluidization zone (31), and the height of the dust baffle (3) is greater than the height of the air cap (2).

2. The ash-blocking and flow-stabilizing structure of the air distribution plate for a circulating fluidized bed boiler according to claim 1, characterized in that, The plane of the dust baffle (3) is perpendicular to the plane of the air distribution plate (1).

3. The ash-blocking and flow-stabilizing structure of the air distribution plate for a circulating fluidized bed boiler according to claim 1, characterized in that, The dust baffle (3) is inclined on the air distribution plate (1), and the included angle α between the dust baffle (3) and the air distribution plate (1) is in the range of 60°≤a<90°.

4. The ash-blocking and flow-stabilizing structure for an air distribution plate in a circulating fluidized bed boiler according to any one of claims 1-3, characterized in that, The maximum height between the top of the dust baffle (3) and the top of the air distribution plate (1) is 300-800 mm.

5. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure according to any one of claims 1-3, characterized in that, The thickness of the dust baffle (3) is 50mm to 300mm.

6. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure according to any one of claims 1-3, characterized in that, The distance between two adjacent dust baffles (3) is 2m to 10m.

7. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure according to any one of claims 1-3, characterized in that, The top of the dust baffle (3) is provided with an arc-shaped chamfer (32).

8. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure according to any one of claims 1-3, characterized in that, The tops of each of the aforementioned dust baffles (3) remain flush.

9. A circulating fluidized bed boiler air distribution plate ash-blocking and flow-stabilizing structure according to any one of claims 1-3, characterized in that, The dust baffles (3) are evenly spaced along the width direction of the air distribution plate (1).

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