A circulating fluidized bed boiler return device

Abstract

The application provides a circulating fluidized bed boiler returning device, and relates to the field of fluidized bed boilers. The circulating fluidized bed boiler returning device comprises a shell and an exhaust air duct in communication, a cavity is arranged in the shell, the bottom of the cavity is arc-shaped, a center wheel disc is rotatably arranged in the shell, and a plurality of arc-shaped hollow rods fixed relative to the center wheel disc are arranged on the center wheel disc. The circulating fluidized bed boiler returning device sets the bottom of the cavity as arc-shaped, replaces the traditional L or U type, continuously contacts the arc surface with the rotating scraping head, and can clean the arc-shaped bottom once a week, so that the flow field dead angle is eliminated, the fine ash removal rate is improved, the coarse particle retention amount is reduced, no additional power source is needed, manual ash cleaning is not needed during long-time use, the scraping head can collide with the protrusions to cause vibration during the rotation process, and the surface dust and foreign matters are shaken off, and the wear can be automatically compensated when the scraping head is used for a long time.

Description

Technical Field

[0001] This invention relates to the field of fluidized bed boilers, specifically to a circulating fluidized bed boiler return device. Background Technology

[0002] Circulating fluidized bed boilers have a fly ash re-combustion system, i.e., a circulating combustion system. The normal circulation of materials in the circulating fluidized bed boiler combustion system is a prerequisite for the safe and controllable operation of the boiler. The return material device is an important component of its circulating combustion system, playing a key role in the boiler's combustion efficiency and operation regulation. Its reliability is crucial to the normal operation of the circulating fluidized bed boiler. Using the return material system, unburned and large-particle-size high-temperature materials leaving the boiler furnace are collected by the cyclone separator and stably sent back to the high-pressure furnace through the shaking leg and return material device. It also ensures that the high-pressure side gas in the furnace backflows into the cyclone separator as little as possible. Incompletely reacted desulfurizing agent, along with ash and a small amount of unburned fuel particles, is collected by the cyclone separator and returned to the furnace by the return material device, improving the utilization rate of the desulfurizing agent.

[0003] In order to adapt to the material circulation path, the return device of the traditional circulating fluidized bed biomass combustion boiler is mostly designed with an L-shaped or U-shaped structure. The ash of biomass fuel is rich in potassium, sodium and silicon. Under the high temperature environment of the return device, low melting point eutectic is easily formed, which adheres to the wall surface of the L-shaped right angle section and the U-shaped arc section, forming a sticky ash layer. The blockage speed is accelerated, and after blockage, it is necessary to rely on regular cleaning to maintain operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a circulating fluidized bed boiler return device, which solves the problems of easy clogging and the need for regular cleaning to maintain operation after clogging.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a circulating fluidized bed boiler return device, comprising a connected shell and an exhaust duct, wherein the shell is provided with a cavity, the bottom of the cavity is arc-shaped, a central wheel is rotatably installed in the shell, and a number of sets of arc-shaped hollow rods fixed relative to it are installed on the central wheel, and an arc-shaped air plate is fixedly installed between each set of arc-shaped hollow rods, wherein one of the arc-shaped air plates is located directly below the air inlet end of the shell;

[0006] Each arc-shaped hollow rod has an arc-shaped tube head slidably connected to one end away from the central wheel. Each set of arc-shaped tube heads has a scraper installed at one end. The scraper contacts the arc surface at the bottom of the cavity during rotation and is used to push the residue deposited at the bottom of the cavity to the exhaust duct.

[0007] Preferably, an exhaust hopper is installed at the air inlet of the housing. The exhaust hopper is a rectangular funnel-shaped structure that is wider at the top and narrower at the bottom. Its upper end is fixed to the housing, and its bottom is located above one of the arc-shaped air plates.

[0008] Preferably, the exhaust hopper has two symmetrical elastic plates A fixedly connected inside, and the free ends of the two elastic plates A are fixedly connected to sealing plates, with the two sealing plates in contact with each other.

[0009] Preferably, two sets of symmetrical elastic plates B are fixedly connected to the air inlet of the housing, and the other end of each set of elastic plates B is fixed to the bottom of the exhaust hopper.

[0010] Preferably, the exhaust bucket includes a head, a connecting part, and a tail that are fixed in sequence. The head and tail are made of rigid materials, the connecting part is made of flexible materials, and the tail of the exhaust bucket is located in a cavity, where the scraper head collides with the tail when it rotates.

[0011] Preferably, the arc-shaped tube head is provided with a limiting groove, and a limiting strip is fixedly connected in the arc-shaped hollow rod, with the limiting strip slidably connected to the limiting groove.

[0012] Preferably, the interior of the arc-shaped hollow rod is provided with several magnets. One magnet near the arc-shaped tube head is fixed to the arc-shaped tube head, one magnet away from the arc-shaped tube head is fixed to the arc-shaped hollow rod, and the remaining magnets are slidably connected to the arc-shaped hollow rod. There is a magnetic repulsion between every two adjacent magnets.

[0013] Preferably, the cross-section of one end of the scraper head is triangular and the cross-section of the other end is circular. The circular end has a protruding structure, and a spring is installed between the protruding part and the arc-shaped wind plate. The spring is in a stretched state.

[0014] Preferably, the interior of the cavity has a sloping structure connected to its arc surface.

[0015] Preferably, a plurality of protrusions are fixedly connected inside the cavity, and the cross-section of the protrusions is arc-shaped.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the bottom of the cavity is set to be arc-shaped, replacing the traditional L or U shape. With the continuous contact of the rotating scraper head with the arc surface, the bottom of the arc can be thoroughly cleaned every time the scraper head rotates, eliminating dead corners in the flow field, improving the fine dust removal rate, and reducing the amount of coarse particles retained. No additional power source is required, and no manual dust cleaning is required during long-term use. During the rotation of the scraper head, it can collide with the protrusion to cause vibration, shaking off the dust and foreign objects on the surface. When the scraper head wears out after long-term use, it can automatically compensate for the wear. Moreover, when the incoming fluidizing air volume is small, the sealing plate can close until the air pressure increases and the sealing plate opens, ensuring that the scraper head can rotate and perform scraping and cleaning work regardless of whether the incoming fluidizing air volume is large or small. Attached Figure Description

[0017] Figure 1 This is a front view of the casing of the present invention;

[0018] Figure 2 This is a cross-sectional view of the front view of the housing of the present invention;

[0019] Figure 3 This is a cross-sectional view of the internal structure of the housing of the present invention;

[0020] Figure 4 This is a partial cross-sectional view of the arc-shaped hollow rod of the present invention;

[0021] Figure 5 This is a sectional view of the exhaust hopper of the present invention from the front view.

[0022] Figure 6 For the present invention Figure 5 Enlarged schematic diagram of the structure at point A in the middle;

[0023] Figure 7 This is a schematic diagram of the arc-shaped wind vane of the present invention;

[0024] Figure 8 This is a schematic diagram of the scraper head of the present invention;

[0025] Figure 9 This is a cross-sectional view of the front view of the scraper head of the present invention;

[0026] Figure 10 This is a schematic diagram of the exhaust hopper of the present invention.

[0027] The components are as follows: 1. Shell; 2. Exhaust duct; 3. Cavity; 4. Central wheel; 5. Arc-shaped hollow rod; 6. Arc-shaped wind vane; 7. Arc-shaped pipe head; 8. Scraper; 9. Exhaust hopper; 901. Head; 902. Connecting part; 903. Tail; 10. Elastic sheet A; 11. Sealing plate; 12. Elastic sheet B; 13. Limiting groove; 14. Limiting strip; 15. Magnet; 16. Protrusion. Detailed Implementation

[0028] like Figures 1-10As shown, a circulating fluidized bed boiler return device includes a shell 1 and an exhaust duct 2 connected to each other. The air inlet end of the shell 1 is used to connect to the shaking leg of the biomass combustion boiler. The shell 1 has a cavity 3 inside, and the bottom of the cavity 3 is arc-shaped. The interior of the cavity 3 has an inclined structure connected to its arc surface. The inclined structure connected to the arc surface of the cavity 3 can guide the residue pushed by the scraper head 8 to slide smoothly along the inclined surface to the exhaust duct 2, avoiding the accumulation of residue at the corner of the bottom of the arc surface of the cavity 3, and solving the problem of secondary ash blockage caused by scraping without discharge. Several protrusions 16 are fixedly connected inside the cavity 3. The cross section of the protrusions 16 is arc-shaped. When the scraper head 8 collides with the protrusions 16, it can generate vibration, shaking off the dust and foreign objects adhering to the scraper head 8. The vibration force can be transmitted to the arc-shaped hollow rod 5 and the arc-shaped air plate 6, shaking off the dust and foreign objects on the surface.

[0029] A central wheel 4 is rotatably mounted inside the housing 1. Several sets of fixed, arc-shaped hollow rods 5 are mounted on the central wheel 4. Each arc-shaped hollow rod 5 contains several magnets 15. One magnet 15 near the arc-shaped tube head 7 is fixed to the arc-shaped tube head 7, and another magnet 15 away from the arc-shaped tube head 7 is fixed to the arc-shaped hollow rod 5. The remaining magnets 15 are slidably connected to the arc-shaped hollow rod 5. Magnetic repulsion exists between every two adjacent magnets 15. The sliding contact of multiple sets of magnets 15 and the superposition of magnetic repulsion allow for automatic adjustment of the extension and retraction amount based on the force applied to the arc-shaped tube head 7, such as when the scraper head 8 encounters hard residue impact. When the scraper head 8 wears, it can automatically compensate for wear, extending the replacement cycle of the scraper head 8 and reducing maintenance frequency. To reduce costs, each set of curved hollow rods 5 is fixedly equipped with a curved air vane 6. One of the curved air vanes 6 is located directly below the air inlet of the housing 1. An exhaust hopper 9 is installed at the air inlet of the housing 1. The exhaust hopper 9 is a rectangular funnel-shaped structure that is wider at the top and narrower at the bottom. Its upper end is fixed to the housing 1, and its bottom is located above one of the curved air vanes 6. The rectangular funnel-shaped exhaust hopper 9 can accurately converge the airflow and material at the air inlet of the housing 1, avoiding the power waste caused by airflow dispersion, so that the airflow can act efficiently on the curved air vane 6 below, improving the rotation efficiency of the central wheel 4. The bottom of the exhaust hopper 9 is located above the curved air vane 6, which can guide the material to slide down along the inner wall of the exhaust hopper 9 into the cavity 3, reducing material flight. To prevent localized accumulation caused by splashing and to avoid direct airflow impact on the residue at the bottom of cavity 3, thus reducing the probability of secondary adhesion of residue, two symmetrical elastic plates A10 are fixedly connected inside the exhaust hopper 9. Each of the free ends of the two elastic plates A10 is fixedly connected to a sealing plate 11. The two sealing plates 11 are in contact. When the air pressure inside the exhaust hopper 9 exceeds a predetermined value, the two elastic plates A10 undergo elastic deformation, and the two sealing plates 11 separate, expelling the gas. Under normal conditions, the two sealing plates 11 are in contact, which can block ineffective airflow between the air inlet of the housing 1 and cavity 3, avoiding fluidizing air pressure loss due to air leakage. Two sets of symmetrical elastic plates B12 are fixedly connected at the air inlet of the housing 1. The other end is fixed to the bottom of the exhaust hopper 9. Two sets of symmetrical elastic plates B12 connect the air inlet of the housing 1 to the bottom of the exhaust hopper 9. When the scraper head 8 hits the exhaust hopper 9, the exhaust hopper 9 can be reset. Under the continuous hitting of the scraper head 8, it can generate vibration, causing the residue in the exhaust hopper 9 to fall off and prevent blockage. The exhaust hopper 9 includes a head 901, a connecting part 902 and a tail 903 fixed in sequence. The head 901 and the tail 903 are made of hard material, the connecting part 902 is made of flexible material, and the tail 903 of the exhaust hopper 9 is located in the cavity 3. When the scraper head 8 rotates, it collides with the tail 903. The head 901 and the tail 903 of the exhaust hopper 9 are made of hard material to ensure the structural stability of airflow and material guidance.The connecting part 902 is made of flexible material, which can buffer the impact of the scraper head 8 on the tail 903 of the exhaust hopper 9 when it rotates. The collision between the rotating scraper head 8 and the tail 903 of the exhaust hopper 9 can indirectly cause the tail 903 of the exhaust hopper 9 to vibrate slightly, shaking off the accumulated dust attached to the tail 903. At the same time, it assists the scraper head 8 in cleaning the dead area of ​​residue near the tail 903, further reducing the risk of dust accumulation.

[0030] Each arc-shaped hollow rod 5 has an arc-shaped tube head 7 slidably connected to one end away from the central wheel 4. The arc-shaped tube head 7 has a limiting groove 13 inside, and a limiting strip 14 is fixedly connected to the arc-shaped hollow rod 5. The limiting strip 14 is slidably connected to the limiting groove 13 to prevent the arc-shaped tube head 7 from detaching from the arc-shaped hollow rod 5. The limiting groove 13 of the arc-shaped tube head 7 and the limiting strip 14 of the arc-shaped hollow rod 5 slide in cooperation, ensuring the arc-shaped tube head 7's freedom of movement while effectively preventing it from falling off due to vibration, particle impact, or long-term use. This avoids unblocking failure or material jamming caused by component detachment. Each set of arc-shaped tube heads 7 has a scraper head 8 installed at one end. One end of the scraper head 8 has a triangular cross-section, and the other end has a circular cross-section. The circular end has a protruding structure, and a spring is installed between the protruding part and the arc-shaped wind plate 6. The spring is in a stretched state. The triangular section end of the scraper head 8 has a sharp scraping edge, which can efficiently remove the hard residue that has adhered to the bottom of the cavity 3. The circular section end, together with the raised structure and the tensioned spring, can provide continuous adhesion force for the scraper head 8, ensuring that the scraper head 8 is always in contact with the arc surface of the cavity 3, avoiding the problem of missed scraping caused by wear of the scraper head 8. During the rotation, the scraper head 8 contacts the arc surface at the bottom of the cavity 3 and is used to push the residue deposited at the bottom of the cavity 3 to the exhaust duct 2. The airflow in the return device, such as fluidizing air, can drive the central wheel 4 to rotate, thereby making the scraper head 8 rotate. No additional power source is required, reducing energy consumption and the risk of power component failure under high temperature environment. During the rotation of the scraper head 8, it can actively push the residue deposited at the bottom of the cavity 3 to the exhaust duct 2, preventing the problem of dust accumulation and blockage at the arc bottom of the return device, ensuring smooth material conveying channel and improving return stability.

[0031] In operation, the air inlet of the device housing 1 is connected to the biomass combustion boiler. The high-temperature circulating ash separated by the separator enters the housing 1 along with the fluidizing air. First, it passes through a rectangular funnel-shaped exhaust hopper 9 (wider at the top, narrower at the bottom). When the amount of gas entering is low, the air pressure is also low. The exhaust hopper 9 precisely gathers the dispersed airflow and material, guiding it down the hopper wall to the lower cavity 3, preventing material splashing and airflow waste. At this time, the elastic plate A10 and the sealing plate 11 are in a normally closed state, blocking ineffective airflow between the air inlet and the cavity 3. When the air pressure exceeds a predetermined value, the sealing plate 11 opens, and the fluidizing air is discharged. The gathered fluidizing air directly acts on the arc-shaped wind plate 6 located directly below the air inlet. The airflow thrust drives the arc-shaped wind plate 6 to rotate around the central wheel 4, thereby driving the entire central wheel 4 to rotate. No additional motor or hydraulic power is required. 4. Simultaneously drive multiple sets of arc-shaped hollow rods 5 to rotate. The end of the arc-shaped hollow rod 5 away from the wheel is slidably connected to the arc-shaped tube head 7 through the limiting groove 13 and the limiting strip 14. The scraper head 8 at the end of the arc-shaped tube head 7 continuously contacts the arc-shaped bottom of the cavity 3 during the rotation process. The triangular section end scraper head 8 can break off the hard residue that has been stuck together. The circular section end and the tension spring provide continuous adhesion force for the scraper head 8, ensuring that the scraper head 8 can still fit with the arc surface after wear. Multiple sets of magnets 15 in the arc-shaped hollow rod 5 can automatically adjust the extension and retraction of the arc-shaped tube head 7 according to the force on the scraper head 8, such as when encountering hard residue impact, to avoid the scraper head 8 getting stuck, and at the same time compensate for the wear of the scraper head 8. The arc-shaped protrusion 16 in the cavity 3 collides with the rotating scraper head 8, and the resulting vibration force can shake off the fine dust adhering to the scraper head 8, the arc-shaped hollow rod 5 and the surface of the air plate, preventing the reduction of cleaning efficiency caused by dust adhering to the components.

[0032] Next, the residue pushed by scraper head 8 is guided by the inclined structure of cavity 3 and slides smoothly along the inclined surface to exhaust duct 2, avoiding accumulation at the corner of the arc bottom. At the same time, if the air pressure in exhaust hopper 9 exceeds the predetermined value due to local ash blockage, elastic plate A10 deforms, causing sealing plate 11 to separate and release pressure, preventing excessive air pressure from damaging shell 1 or causing flue gas backflow. Elastic plate B12 connects shell 1 and bottom of exhaust hopper 9. When scraper head 8 hits exhaust hopper 9, elastic plate B12 causes exhaust hopper 9 to reset and vibrate, shaking off residue in the hopper. Flexible connection part 902 of exhaust hopper 9 can buffer the collision impact between scraper head 8 and hopper body to avoid hard damage. At the same time, the tail 903 vibrates to assist in cleaning nearby residue dead zones. Limiting strip 14 and limiting groove 13 slide together to ensure that arc-shaped pipe head 7 does not fall off during extension and vibration, avoiding secondary blockage caused by component detachment.

[0033] It should be noted that, in response to the problems of blockage at the bends of traditional L-shaped or U-shaped return material devices, such as passive blockage removal, reliance on shutdown for cleaning, and cascading failures, this device designs the bottom of cavity 3 as arc-shaped, replacing the traditional L-shaped or U-shaped design. Combined with the continuous contact of the rotating scraper head with the arc surface, it can efficiently break down the low-melting-point sticky ash layer formed by biomass fuel, reducing the residence time of sticky ash at the bottom of the arc and extending the cleaning cycle. With the continuous contact of the rotating scraper head 8 with the arc surface, each rotation of the scraper head 8 can perform a complete cleaning of the bottom of the arc, eliminating dead zones in the flow field. The fluidized air-driven dynamic cleaning improves the fine ash removal rate and reduces the amount of coarse particles retained compared to traditional static fluidization. The exhaust hopper 9 gathers airflow, allowing the fluidized air to act efficiently on the arc-shaped air plate 6, ensuring that the central wheel 4 can rotate effectively. The scraper head 8 can promptly remove freshly settled ash particles, preventing the formation of a sticky ash layer. The inclined structure of cavity 3 guides the rapid discharge of residue, avoiding the secondary accumulation caused by scraping without discharge in traditional arc-shaped bottom designs.

[0034] Traditional return material devices often experience blockages that disrupt material circulation, leading to a chain reaction of malfunctions in biomass boilers. Blockages in traditional devices interrupt ash circulation, resulting in thinner bed layers, sudden temperature increases, coking, and decreased combustion and desulfurization efficiency. In this device, the rotating scraper head 8 actively clears blockage risks, ensuring a smooth ash circulation channel and preventing sudden changes in bed thickness. The magnet 15's compensation and spring-loaded design ensure that the scraper head 8 remains in contact with the arc surface for extended periods, effectively clearing blockages even after wear. This reduces circulation interruptions caused by blockage failure and improves combustion efficiency.

[0035] Finally, it should be noted that since the inclined surface inside cavity 3 is connected to the arc surface, the dust on the inclined surface will fall along the inclined surface to the arc surface, and then be discharged under the action of scraper head 8. Moreover, when scraper head 8 is separated from the arc surface, it will extend a certain distance and contact the inclined surface during rotation. When scraper head 8 moves from the inclined surface to the arc surface, under the pressure of the inclined surface, scraper head 8 will re-adhere to the arc surface, ensuring that scraper head 8 is in close contact with the arc surface to improve the scraping effect.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circulating fluidized bed boiler return device, comprising a connected shell (1) and an exhaust duct (2), characterized in that: The housing (1) has a cavity (3) inside, the bottom of the cavity (3) is arc-shaped, a central wheel (4) is rotatably installed in the housing (1), and several sets of arc-shaped hollow rods (5) fixed relative to it are installed on the central wheel (4). An arc-shaped wind plate (6) is fixedly installed between each set of arc-shaped hollow rods (5), and one of the arc-shaped wind plates (6) is located directly below the air inlet end of the housing (1). Each arc-shaped hollow rod (5) has an arc-shaped tube head (7) slidably connected to one end away from the central wheel (4). Each set of arc-shaped tube heads (7) has a scraper (8) installed at one end. The scraper (8) contacts the arc surface at the bottom of the cavity (3) during rotation and is used to push the residue deposited at the bottom of the cavity (3) to the exhaust duct (2). An exhaust hopper (9) is installed at the air inlet of the housing (1). The exhaust hopper (9) is a rectangular funnel-shaped structure that is wider at the top and narrower at the bottom. Its upper end is fixed to the housing (1), and its bottom is located above one of the arc-shaped wind plates (6). The exhaust hopper (9) has two symmetrical elastic plates A (10) fixedly connected inside. The free ends of the two elastic plates A (10) are fixedly connected to sealing plates (11), and the two sealing plates (11) are in contact with each other. Two sets of symmetrical elastic plates B (12) are fixedly connected to the air inlet of the housing (1), and the other ends of the two sets of elastic plates B (12) are fixed to the bottom of the exhaust hopper (9). The arc-shaped tube head (7) is provided with a limiting groove (13), and a limiting strip (14) is fixedly connected in the arc-shaped hollow rod (5). The limiting strip (14) is slidably connected to the limiting groove (13). The interior of the arc-shaped hollow rod (5) is provided with several magnets (15). One magnet (15) close to the arc-shaped tube head (7) is fixed to the arc-shaped tube head (7), and one magnet (15) away from the arc-shaped tube head (7) is fixed to the arc-shaped hollow rod (5). The remaining magnets (15) are slidably connected to the arc-shaped hollow rod (5). There is a magnetic repulsion between every two close magnets (15). The cross-section of one end of the scraper head (8) is triangular, and the cross-section of the other end is circular. The circular end has a protruding structure, and a spring is installed between the protruding structure and the arc-shaped wind plate (6). The spring is in a stretched state. Several protrusions (16) are fixedly connected inside the cavity (3), and the cross-section of the protrusions (16) is arc-shaped.

2. The circulating fluidized bed boiler return device according to claim 1, characterized in that: The exhaust bucket (9) includes a head (901), a connecting part (902) and a tail (903) fixed in sequence. The head (901) and the tail (903) are made of hard material, and the connecting part (902) is made of flexible material. The tail (903) of the exhaust bucket (9) is located in the cavity (3), and the scraper (8) collides with the tail (903) when it rotates.

3. The circulating fluidized bed boiler return device according to claim 1, characterized in that: The cavity (3) has an inclined surface structure connected to its arc surface inside.

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