Bell-shaped hood of biomass circulating fluidized bed boiler

Abstract

The invention discloses a biomass circulating fluidized bed boiler bell-jar-shaped hood which comprises a hood outer cover, an air distribution cavity is formed in the hood outer cover, a plurality of air distribution holes are evenly distributed in the lower portion of the hood outer cover in the circumferential direction, and a clamping groove is further formed in the hood outer cover; the split type air pipe comprises an air pipe upper section and an air pipe lower section which are detachably connected, the air pipe upper section and the air pipe lower section are in sealed butt joint through threaded connection, the air pipe upper section is provided with a clamping block matched with the clamping groove so that the outer cover and the air pipe upper section can be axially fixed through rotation, and the air pipe lower section is fixed to the air distribution plate. The fixing part comprises a head part and a rod part which are connected, the rod part penetrates through the hood outer cover and is in threaded connection with the air pipe upper section, and the head part abuts against the hood outer cover. According to the design, through an anti-locking connection structure and a modular replacement scheme, the fluidization uniformity is remarkably improved, the maintenance cost is reduced, the downtime is shortened, and the device is suitable for high-ash-content and high-abrasion biomass fuel boiler scenes and has efficient combustion and long-period operation stability.

Description

Technical Field

[0001] This invention belongs to the field of circulating fluidized bed technology, specifically relating to a bell-shaped wind cap for a biomass circulating fluidized bed boiler. Background Technology

[0002] In the operation of circulating fluidized bed boilers, the air cap is a key component, and its performance directly affects the boiler's stability and efficiency. The main function of the air cap is to ensure uniform air distribution through reasonable design resistance, avoiding the formation of fluidization dead zones and preventing slag leakage into the air chamber while ensuring uniform material fluidization. Its design must adapt to the boiler's operating requirements under different loads, ensuring a moderate outlet air velocity to reduce wear between air caps, lower the risk of blockage, facilitate maintenance, and extend service life.

[0003] Because biomass fuel contains a lot of impurities such as iron nails and stones, these impurities can cause significant wear on the air caps during the operation of biomass fuel circulating fluidized bed boilers. At the same time, the debris entering the air cap outlets can adhere at high temperatures, causing blockages and reducing the fluidization effect of the boiler. This directly affects the unit's load-carrying capacity and, in severe cases, can lead to unplanned unit shutdowns.

[0004] Traditional wind caps are mostly integrally cast structures, requiring disassembly of the entire cap or cleaning of accumulated dust in the air chamber for replacement, which is time-consuming and labor-intensive. Small-diameter air outlets are prone to clogging in fuels with high ash content or highly sticky particles, necessitating regular manual unclogging and increasing maintenance costs. The bell-shaped wind cap, with its double-layer structure (air duct + outer bell shell), allows for separate replacement of the bell shell, significantly reducing maintenance costs and downtime.

[0005] The wind cap housing and the air duct are connected by threads, which makes installation and disassembly relatively convenient initially. However, because the wind cap is exposed to high temperature and high wear environment for a long time, it is prone to deformation or jamming. The threaded connection is also prone to deformation or jamming, and forced disassembly may damage the components.

[0006] Traditional air distribution panels and ducts are manufactured using an integrated casting process. While this integral molding ensures structural strength, the inner wall of the duct is prone to wear and even perforation due to particle erosion under high-temperature and high-wear conditions. Because the integrated design makes it non-removable, the entire inner duct needs to be replaced after wear. Maintenance requires cutting the air distribution panel or removing the entire set of air caps, which is time-consuming, labor-intensive, and can easily damage the fire-resistant layer and the air chamber seal. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides an easily replaceable bell-shaped air cap for biomass circulating fluidized bed boilers, effectively ensuring efficient combustion and long-term stability of the circulating fluidized bed boiler.

[0008] The present invention adopts the following technical solution:

[0009] A bell-shaped vent cap for a biomass circulating fluidized bed boiler includes:

[0010] The hood cover has an air distribution chamber inside, and multiple air distribution holes are evenly distributed around the lower part of the hood cover. The hood cover also has a slot inside.

[0011] The split-type air duct includes a detachable upper section and a lower section of the air duct. The upper section and the lower section of the air duct are connected by threads to achieve a sealed connection. The upper section of the air duct is provided with a locking block that matches the slot, so that the outer cover and the upper section of the air duct can be axially fixed by rotation. The lower section of the air duct is fixed to the air distribution plate.

[0012] The fixing part includes a head and a rod connected together, the rod passing through the outer cover of the hood and being threadedly connected to the upper section of the duct, and the head abutting against the outer cover of the hood.

[0013] Furthermore, the air distribution hole is inclined, and the opening of the air distribution hole on the inner wall of the wind cap is higher than its opening on the outer wall of the wind cap. The inclination angle of the air distribution hole is 15°±2°.

[0014] Furthermore, the upper section of the duct is provided with a duct hole to communicate with the air distribution chamber, and the diameter of the duct hole is larger than the diameter of the air distribution hole.

[0015] Furthermore, a sealing gasket is provided between the head and the outer cover of the hood, and the sealing gasket is a graphite spiral wound gasket with a temperature resistance range of ≥600℃.

[0016] Furthermore, a limiting plate is provided between the outer cover of the hood and the upper section of the air duct. The limiting plate is fixed to the side wall of the slot to limit the rotation angle of the outer cover.

[0017] Furthermore, the lower end of the upper section of the duct is provided with an external thread, and the upper end of the lower section of the duct is provided with an internal thread; the length of the external thread of the upper section of the duct is not less than 20mm, and the thread profile is a trapezoidal thread.

[0018] Furthermore, a 0.2mm gap is provided between the card slot and the card block, and the card block is made of a high-temperature resistant alloy.

[0019] Furthermore, the head of the fixing part is provided with an internal hexagonal hole.

[0020] A method for installing a bell-shaped vent cap in a biomass circulating fluidized bed boiler includes the following steps:

[0021] S11. Weld and fix the lower section of the duct to the air distribution plate, ensuring that its internal threaded interface faces vertically upward;

[0022] S12. Align the external thread of the upper section of the duct with the internal thread of the lower section of the duct, and tighten to form a sealed connection;

[0023] S13. Align the annular groove at the bottom of the hood cover with the clip on the upper section of the duct, and insert the clip axially into the annular groove through the groove;

[0024] S14. Rotate the outer cover of the wind cap 90° to make the locking block abut against the limiting plate, forming a circumferentially evenly distributed clearance fit;

[0025] S15. Pass the rod of the fixing part through the hood hole and sealing gasket at the top of the hood cover, and screw it into the threaded end of the upper section of the air duct until the head presses against the sealing gasket to complete the axial locking and fixing;

[0026] S16. Introduce primary air to verify the airflow uniformity in the direction of the air distribution hole tilted at 15°±2°.

[0027] Beneficial effects

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The wind cap mainly consists of an axisymmetric bell-shaped wind cap cover and a coaxially connected air duct. An annular air distribution chamber is located inside the wind cap, and the air duct vertically penetrates the top of the wind cap body and extends into the air distribution chamber. Multiple inclined air distribution holes are evenly distributed circumferentially on the lower part of the wind cap cover. These air distribution holes are evenly arranged on the lower part of the wind cap, while the air duct holes are evenly arranged on the upper part of the air duct. The wind cap shell and the air duct are connected by a snap-fit ​​structure and locked in place by a threaded structure at the top. The air duct is divided into detachable upper and lower sections, which are connected by threads.

[0030] The upper part of the air duct is provided with a boss that contacts the lower part of the air cap cover to support the air cap. The boss area is provided with a threaded end. The air cap has an air cap hole for the threaded fixing part to pass through and be threadedly connected to the threaded end. The connection between the fixing part and the air cap hole is sealed.

[0031] The fixing part consists of a head and a threaded rod. The rod has external threads and internal threads at the threaded end. The rod and the threaded end are threadedly connected. A sealing gasket is provided at the position where the head connects to the wind cap.

[0032] The bottom of the hood has a ring-shaped recessed mounting groove, and the lower part of the duct has a convex locking block with an outer diameter slightly smaller than the inner diameter of the mounting groove by 0.2 mm, and a height consistent with the groove depth. The bottom of the outer cover has four evenly distributed small holes, matching the size of the duct locking block. The upper section of the duct passes through these small holes along the bottom of the hood cover. A limiting plate is added to precisely control the rotation angle between the outer cover and the duct, ensuring the stability of the locking structure. Once the locking block reaches the position of the limiting plate, rotation will secure the hood cover to the duct.

[0033] Furthermore, the slots are evenly distributed around the circumference with a spacing of 90°, and the number of locking blocks corresponds accordingly. This makes the connection between the wind cap cover and the air duct more balanced, and vibrations are less likely to cause the wind cap to rotate, effectively preventing the wind cap head from falling off.

[0034] The duct adopts a split threaded connection structure. The lower section of the duct is fixed to the air distribution plate base by welding. Its upper end is machined with an internal thread interface, and the lower end of the upper section of the duct is correspondingly provided with an external thread. During installation, the external thread of the upper section of the duct is screwed into the internal thread of the lower section to form a sealed connection. After wear, only the upper section of the duct needs to be rotated and disassembled for replacement. There is no need to damage the welded structure of the air distribution plate. This maintains the strength of the base structure and realizes the rapid modular replacement of the worn section of the inner duct, significantly reducing maintenance complexity and equipment downtime losses.

[0035] The through-flow channel design of its bell-shaped body and coaxial seat tube enhances the pressure distribution capability of the primary air within the air distribution chamber. Combined with the diffusion airflow formed by the circumferentially inclined air distribution holes, it can effectively eliminate fluidization dead zones and enhance bed bottom disturbance, thereby improving gas-solid mixing uniformity and combustion efficiency. The downwardly inclined air distribution holes suppress particle deposition through directional airflow scouring, simultaneously reducing the risk of orifice blockage. The enveloping layout of the bell-shaped structure reduces the direct impact of high-speed airflow on adjacent air caps, significantly alleviating local wear.

[0036] The vent cap is not welded to the duct, and the top of the duct is threaded with a pre-drilled round hole. The thread extends to the top of the duct, preventing bed material from seeping in during normal boiler operation and preventing the vent cap from detaching and leaking slag through the duct. The newly designed connection method features a longer service life for the screw. During shutdown maintenance and replacement, only the fixing part needs to be disassembled, the new vent cap replaced, and the fixing part tightened again, without damaging the duct. This minimizes maintenance workload and shortens the maintenance cycle.

[0037] The lower end of the vent cap is fixed by an axial fit design using an annular groove and a convex locking block. The gap design between the locking block and the groove allows for free compensation of thermal expansion, alleviating thermal stress concentration. The overall solution ensures connection rigidity while also resisting fretting wear and possessing self-slag removal capability, providing a reliable mechanical connection guarantee for the high-frequency maintenance needs and long-term operation of circulating fluidized bed boilers.

[0038] In summary, the present invention has a stable structure, is easy to disassemble and maintain, and has the dual advantages of improving boiler thermal efficiency and extending service life. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a bell-shaped wind cap structure for a biomass circulating fluidized bed boiler according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the windproof hood cover structure;

[0041] Figure 3 This is a schematic diagram of the duct structure.

[0042] The components are as follows: 1. Vent cover; 2. Upper section of duct; 3. Lower section of duct; 4. Air distribution chamber; 5. Vent hole; 6. Fixing part; 7. Head; 8. Rod; 9. Sealing gasket; 10. Duct hole; 11. Hexagonal socket hole; 12. Air distribution hole; 13. Slot; 14. Block; 15. Groove; 16. Internal thread; 17. External thread; 18. Threaded end; 19. Air distribution plate; 20. Limiting plate. Detailed Implementation

[0043] The present invention will now be further described with reference to specific embodiments and accompanying drawings.

[0044] Please see Figures 1 to 3 As shown, this invention provides an easily replaceable air cap for a circulating fluidized bed boiler, comprising an air cap cover 1, an upper section of air duct 2, and a lower section of air duct 3. The air cap cover 1 covers the upper part of the upper section of air duct 2. A locking block 14 is provided on the wall of the upper section of air duct 2, which contacts the locking groove 13 at the lower part of the air cap 1 to support the air cap 1. Four sets of locking grooves and locking blocks are evenly distributed circumferentially with a spacing of 90°. During installation, the locking block 14 on the upper section of air duct 2 inserts into the interior of the air cap along the bottom of the air cap head. The bottom of the air cap cover 1 has a groove 15 of the same size as 14. The locking block 14 reaches the area around the locking groove 13 at the air cap head, rotates, and passes through a limiting plate 20 to determine the position of the air cap shell and the air duct.

[0045] To further secure the vent cap / vent cap cover 1 and the upper section of the duct 2, and to prevent the snap-fit ​​structure from loosening due to the flow field, a head 7 and a threaded rod 8 are used for fixation. A threaded end 18 is provided at the upper part of the upper section of the duct 2. The vent cap 1 has a circular vent cap hole 5 through which a threaded fixing part 6 passes and is threadedly connected to the threaded end 18. The connection between the fixing part 6 and the vent cap hole 5 is sealed. This achieves the connection and fixation of the vent cap / vent cap cover 1 and the upper section of the duct 2, preventing the vent cap / vent cap cover 1 from falling off during hot operation.

[0046] The fixing part 6 consists of a head 7 and a threaded rod 8. The rod 8 has external threads, and the threaded end 18 is a connecting part with internal threads. The rod 8 and the threaded end 18 are threadedly connected. The head 7 is cylindrical, and the diameter of the head 7 is larger than the diameter of the rod 8 and larger than the diameter of the hood hole 5. The head 7 is snapped onto the outside of the hood cover 1. The head 7 has an internal hexagonal hole 11 for easy disassembly of the fixing part 6. The threaded end 18 protrudes from the upper part of the upper section 2 of the duct and is welded to the upper section 2 of the duct or integrally cast.

[0047] Use an Allen wrench to pass the fixing part 6 through the hood hole 5 and connect it to the threaded end 7. A sealing gasket 9 is provided at the position where the head 7 connects to the hood and the hood cover 1.

[0048] The lower part of the vent cap 1 has air distribution holes 12, and the upper part of the duct 2 has duct holes 10. After the vent cap 1 is connected to the upper duct 2, the position of the air distribution holes 12 is lower than the position of the duct holes 10. Multiple inclined air distribution holes 12 are evenly distributed circumferentially on the lower part of the vent cap 1, with the holes extending from the inner wall to the outer wall. The air holes on the vent cap 1 are arranged at a downward inclination of 15°, which can improve the uniformity of material fluidization on the air distribution plate. Air enters from the bottom of the lower duct 3, passes through the duct holes 10 to the air distribution cavity 4 between the vent cap 1 and the upper duct 2, and is then discharged through the air distribution holes 12 into the circulating fluidized bed boiler.

[0049] A sealing gasket 9 is designed at the joint between the fixing part 6 and the wind cap / wind cap cover 1. The head 7 of the fixing part 6 is designed with an internal hexagonal hole 11 for easy installation and removal. Since the thread is designed to extend to the upper end of the upper section 2 of the air duct, it can prevent bed material from seeping in during normal boiler operation. At the same time, it is continuously cooled by the primary air of the boiler during use, and the operating temperature is not high. The screw in the newly designed connection method has a longer service life. When shutting down for maintenance and replacement, only the fixing part 6 needs to be disassembled, a new wind cap / wind cap cover 1 needs to be replaced, and then the fixing part 6 needs to be tightened. This will not damage the upper section 2 of the air duct, resulting in a small workload and a short maintenance cycle.

[0050] The installation method includes the following steps:

[0051] S11. Weld and fix the lower section 3 of the air duct to the air distribution plate 19, ensuring that its internal thread 17 interface is vertically upward;

[0052] S12. Align the external thread 16 of the upper section 2 of the duct with the internal thread 17 of the lower section 3 of the duct, and tighten to form a sealed connection;

[0053] S13. Align the annular groove 13 at the bottom of the hood cover 1 with the locking block 14 of the upper section 2 of the air duct, and insert the locking block 14 axially into the annular groove 13 through the groove 15.

[0054] S14. Rotate the outer cover 1 of the hood 90° so that the locking block 14 abuts against the limiting plate 20 to form a circumferentially evenly distributed clearance fit;

[0055] S15. Pass the rod part 8 of the fixing part 6 through the hood hole 5 and the sealing gasket 9 at the top of the hood cover 1, and screw it into the threaded end 18 of the upper section 2 of the air duct until the head 7 presses the sealing gasket 9 to complete the axial locking and fixing.

[0056] S16. Introduce primary air to verify the airflow uniformity in the direction of the air distribution hole 12 tilted at 15°±2°.

[0057] The duct employs a split-type threaded connection design, eliminating the need to damage the air distribution plate and refractory bricks, thus enabling the replacement of the upper duct section 2. The lower end of the upper duct section 2 is machined with external threads 16, while the lower duct section 3 is welded to the air distribution plate 19, with corresponding internal threads 17 at its upper end. During installation, the external thread of the upper duct section is screwed into the internal thread of the lower duct to form a sealed connection. When replacing the upper duct section 2, a special tool is used to loosen the threaded structure, and the old duct is smoothly ejected using a guide pin. The new duct is then manually tightened to ensure a uniform fit of the sealing surface. This design maintains the integrity of the welded structure of the air distribution plate while enabling rapid replacement of worn sections of the inner duct, significantly reducing maintenance complexity and equipment downtime losses.

[0058] The replacement method includes the following steps:

[0059] S21. Disassemble the fixing part 6: Loosen the rod part 8 through the internal hexagonal hole 11 and remove the sealing gasket 9;

[0060] S22. Rotate the wind cap cover 190° in the opposite direction so that the locking block 14 is aligned with the groove 15 and then axially separate the cover;

[0061] S23. Unscrew the worn upper section 2 of the duct, replace it with a new duct body and repeat steps S12-S16 of the installation method;

[0062] S24. The air distribution plate 19 and the lower section 3 of the air duct remain in the same welded state.

[0063] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A bell-shaped vent cap for a biomass circulating fluidized bed boiler, characterized in that, include: The hood cover has an air distribution chamber inside, and multiple air distribution holes are evenly distributed around the lower part of the hood cover. The hood cover also has a slot inside. The split-type air duct includes a detachable upper section and a lower section of the air duct. The upper section and the lower section of the air duct are connected by threads to achieve a sealed connection. The upper section of the air duct is provided with a locking block that matches the slot, so that the outer cover and the upper section of the air duct can be axially fixed by rotation. The lower section of the air duct is fixed to the air distribution plate. The fixing part includes a head and a rod connected together, the rod passing through the outer cover of the hood and being threadedly connected to the upper section of the duct, and the head abutting against the outer cover of the hood.

2. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, The air distribution hole is inclined, and the opening of the air distribution hole on the inner wall of the wind cap is higher than its opening on the outer wall of the wind cap. The inclination angle of the air distribution hole is 15°±2°.

3. The air cap for a biomass circulating fluidized bed boiler according to claim 2, characterized in that, The upper section of the duct is provided with a duct hole to communicate with the air distribution chamber, and the diameter of the duct hole is larger than the diameter of the air distribution hole.

4. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, A sealing gasket is provided between the head and the outer cover of the hood. The sealing gasket is a graphite spiral wound gasket with a temperature resistance range of ≥600℃.

5. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, A limiting plate is provided between the outer cover of the hood and the upper section of the duct. The limiting plate is fixed to the side wall of the slot to limit the rotation angle of the outer cover.

6. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, The upper section of the duct is provided with an external thread at its lower end, and the lower section of the duct is provided with an internal thread at its upper end; the length of the external thread of the upper section of the duct is not less than 20mm, and the thread profile is a trapezoidal thread.

7. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, There is a 0.2mm gap between the card slot and the card block, and the card block is made of high temperature resistant alloy.

8. The air cap for a biomass circulating fluidized bed boiler according to claim 1, characterized in that, The head of the fixing part is provided with an internal hexagonal hole.

9. A method for installing a bell-shaped vent cap in a biomass circulating fluidized bed boiler, characterized in that, Includes the following steps: S11. Weld and fix the lower section of the duct to the air distribution plate, ensuring that its internal threaded interface faces vertically upward; S12. Align the external thread of the upper section of the duct with the internal thread of the lower section of the duct, and tighten to form a sealed connection; S13. Align the annular groove at the bottom of the hood cover with the clip on the upper section of the duct, and insert the clip axially into the annular groove through the groove; S14. Rotate the outer cover of the wind cap 90° to make the locking block abut against the limiting plate, forming a circumferentially evenly distributed clearance fit; S15. Pass the rod of the fixing part through the hood hole and sealing gasket at the top of the hood cover, and screw it into the threaded end of the upper section of the air duct until the head presses against the sealing gasket to complete the axial locking and fixing; S16. Introduce primary air to verify the airflow uniformity in the direction of the air distribution hole tilted at 15°±2°.

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