A circulating fluidized bed boiler system suitable for biomass fuel and a feeding device thereof

Abstract

This utility model provides a circulating fluidized bed boiler system and its feeding device suitable for biomass fuel. The feeding device includes a screw feeder and a drum feeder. The inlet of the drum feeder is connected to the outlet of the screw feeder. The drum feeder is provided with a first outlet and a second outlet. The first outlet is connected to the furnace, and the second outlet is connected to a crusher. The drum feeder includes an inner cylinder and an outer cylinder arranged coaxially. The inner wall of the outer cylinder is provided with diamond-shaped protrusions, and the inner cylinder is a screen with adjustable aperture. A rotating scraper assembly is arranged coaxially with the inner cylinder, and a high-frequency vibrator is provided on the outer wall of the inner cylinder. The two ends of the drum are provided with a labyrinth seal and a nitrogen curtain double sealing structure. Relying on the boiler body system, the problem of poor flowability and easy bridging of biomass fuel is solved by improving the feeder. No major modifications to the boiler body are required, and the amount of engineering work is small. This feeder has a significant effect on improving the ash balance characteristics of the boiler and enhancing the boiler safety. The system operates reliably and stably, and the maintenance workload is small.

Description

Technical Field

[0001] This utility model belongs to the field of circulating fluidized bed boiler fuel supply technology, and specifically relates to a circulating fluidized bed boiler system and its feeding device suitable for biomass fuel. Background Technology

[0002] CFB boilers are characterized by wide fuel adaptability, good environmental performance, and easy ash utilization, making them easy to implement in large-scale engineering applications and widely used in my country's thermal power and chemical industries. However, when burning biomass fuels, traditional screw feeders face technical challenges such as material compression and blockage, adhesion and entanglement due to the unique physicochemical properties of biomass fuels. Compared to traditional fossil fuels, biomass fuels exhibit significant differences in physical characteristics, primarily high moisture content, loose and porous structure, and diverse morphologies. For example, when straw is loosely piled, it easily forms an arching effect, causing material to become bridging; fine particles such as sawdust and rice husks absorb moisture, leading to increased adhesion due to increased moisture content; and bark and twig blocks, due to their irregular geometric shapes, easily cause mechanical blockage in the conveying channel.

[0003] Traditional screw feeders, based on the axial pushing principle generated by the rotation of screw blades, exhibit significant technical limitations when processing biomass fuel. Taking high-moisture biomass as an example, its viscous nature causes irreversible adhesion between the material and the screw blade surface and the inner wall of the feed cylinder during rotation. With accumulated operating time, the thickness of the adhesion layer increases exponentially, leading to a reduction in the effective conveying cross-sectional area, a significant increase in mechanical resistance, and ultimately, blockage of the material conveying channel. For low-density, high-porosity fragments, the axial thrust generated by the screw blades is insufficient for uniform material conveying, easily causing material compression and entanglement inside the feed cylinder, especially at the junction of the screw shaft and end cap, where mechanical jamming can occur, causing feed system interruptions. These technical problems directly affect the continuity and stability of the feed system. Frequent blockages force operators to perform emergency shutdowns for maintenance, resulting in periodic interruptions in boiler fuel supply; and the flow fluctuations caused by adhesion and entanglement lead to unsteady boiler combustion conditions. When fuel supply is insufficient, the furnace combustion temperature cannot be maintained under design conditions; excessive supply leads to localized oxygen-deficient combustion, resulting in increased black smoke emissions and unburned carbon loss. This unsteady combustion mode not only reduces boiler thermal efficiency but also significantly increases equipment maintenance costs and workload. Furthermore, due to the large fluctuations in biomass density, existing biomass screw feeder technology suffers from problems such as large dynamic metering errors (simple weight metering errors are generally >5%), easily worn or expensive commonly used seals, and limited adaptability. While boiler optimization and retrofitting can solve some problems inherent in early design and manufacturing, the retrofitting project involves a large workload, long construction period, and high investment costs. Moreover, because the retrofitting may involve adjustments to key components and boiler heating surfaces, the technical difficulty and risks are high.

[0004] For this type of circulating fluidized bed boiler, in order to solve the problems of clogging, inaccurate metering, sealing failure and poor adaptability of biomass feeding, this utility model aims to solve the above-mentioned technical bottlenecks and provide a low-cost and highly adaptable feeding solution without major modifications to the boiler body. Utility Model Content

[0005] To address the problems existing in the prior art, this utility model provides a feeding device suitable for circulating fluidized bed boilers using biomass fuel. By optimizing the feeding system structure and implementing anti-clogging design, the feeding stability is improved and the combustion conditions are optimized, thereby achieving efficient and long-cycle operation of the circulating fluidized bed boiler.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a feeding device for a circulating fluidized bed boiler suitable for biomass fuel, comprising a screw feeder and a drum feeder. The inlet of the drum feeder is connected to the outlet of the screw feeder. The drum feeder is provided with a first outlet and a second outlet. The first outlet is connected to the furnace, and the second outlet is connected to a crusher. The drum feeder includes an inner cylinder and an outer cylinder arranged coaxially. The inner wall of the outer cylinder is provided with diamond-shaped protrusions, and the inner cylinder is a screen with adjustable aperture. A rotating scraper assembly is arranged coaxially with the inner cylinder, and a high-frequency vibrator is provided on the outer wall of the inner cylinder. The two ends of the drum are provided with a double sealing structure of labyrinth seal and nitrogen curtain.

[0007] As a further optimization, a silo is also included, with a manual gate valve, a rotary feeder valve and a screw feeder sequentially installed at the outlet of the silo along the biomass fuel flow direction.

[0008] As a further optimization, the height of the rhomboid protrusions is 10-30mm, they are distributed in a spiral array, and the spacing between the rhomboid protrusions is 5-15mm.

[0009] As a further optimization, an expansion joint is installed between the outlet of the roller feeder and the inlet of the furnace.

[0010] As a further optimization, the rotary scraper assembly is connected to a separate rotary motor.

[0011] As a further optimization, the diamond-shaped protrusions are arranged in a spiral pattern.

[0012] As a further optimization, both the high-frequency vibrator and the infrared moisture detection module are connected to the input of the control system, while the high-frequency vibrator is connected to the output of the control system.

[0013] As a further optimization, the screw feeder is equipped with an infrared moisture detection module and a material metering sensor.

[0014] As a further optimization, a buffer chamber is installed between the inlet of the roller feeder and the outlet of the screw feeder.

[0015] This utility model also provides a circulating fluidized bed boiler system suitable for biomass fuel, and the feeding device includes the above-mentioned circulating fluidized bed boiler feeding device suitable for biomass fuel.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: by improving the feeder, the problems of poor flowability and easy bridging of biomass fuel are solved, no major modifications to the boiler body are required, the amount of engineering work is small, and the investment cost is low. The drum feeder described in this application has a significant effect on improving the ash balance characteristics of the boiler and enhancing the boiler safety. Compared with the traditional feeding method, the blockage rate is reduced by 90%, the air leakage rate is <0.5%, and the system operates reliably and stably with little maintenance workload.

[0017] Furthermore, the dimensions of the rhomboid protrusions are designed to optimize the material agitation trajectory, and the spacing is designed to balance conveying efficiency and anti-clogging requirements; the spiral array distribution guides the axial movement of the material. The helical arrangement of the rhomboid protrusions propels the material along the spiral path, extending the residence time inside the drum and improving screening uniformity.

[0018] Furthermore, an expansion joint is installed at the furnace inlet to compensate for displacement deviations caused by thermal expansion, reduce stress on the connection structure, and prevent leakage.

[0019] Furthermore, the scraper assembly is connected to a separate motor, allowing for independent control of the scraper speed. This adapts to different material characteristics and avoids screen clogging caused by coupling with the drum speed.

[0020] Furthermore, the screw feeder is equipped with an infrared moisture detection module and a material metering sensor, and a buffer chamber is set between the inlet of the roller feeder and the outlet of the screw feeder. This can help achieve accurate material metering, and if the material does not meet the dryness requirements temporarily, the material will first enter the buffer chamber, and then continue to enter the roller feeder when the subsequent material meets the dryness requirements. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a biomass fuel drum feeder system for a circulating fluidized bed boiler.

[0022] Figure 2 This is a schematic diagram of a biomass fuel roller feeder for a circulating fluidized bed boiler.

[0023] In the attached diagram, 1-hopper, 2-manual gate valve, 3-rotary feeder valve, 4-screw feeder, 5-drum feeder, 51-diamond protrusion, 52-rotary scraper assembly, 53-high frequency vibrator, 54-double sealing structure of labyrinth seal and nitrogen curtain, 6-expansion joint, 7-furnace chamber. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0025] Addressing the characteristics of biomass fuel—high moisture content, loose texture, and susceptibility to clogging—and the limitations of existing screw feeder technology—such as material compression and clogging, large metering errors, easy seal wear, and limited adaptability—this paper proposes a solution without major modifications to the circulating fluidized bed (CFB) boiler itself. This solution relies on structural optimization and anti-clogging design of the CFB boiler feeding device, specifically tailored to biomass fuel. The main objectives are as follows: First, to improve feeding stability and accuracy through a dynamic metering system, optimizing combustion conditions; second, to achieve a 90% reduction in clogging rate and an air leakage rate of <0.5% through anti-clogging design and a dual sealing mechanism, improving boiler safety; and third, to improve fuel flowability through a drum feeder, significantly increasing biomass fuel return efficiency, thereby reducing energy consumption and extending boiler operating cycles.

[0026] In the circulating fluidized bed boiler feeding device suitable for biomass fuel provided in this application, the outlet of the silo 1 is sequentially equipped with a manual gate valve 2, a rotary feed valve 3, and a screw feeder 4 along the biomass fuel flow direction. The outlet of the screw feeder 4 is connected to the inlet of a drum feeder 5, and the outlet of the drum feeder 5 is connected to the furnace 7. The drum feeder 5 includes an inner cylinder and an outer cylinder arranged coaxially. The surface of the inner cylinder is provided with diamond-shaped protrusions 51, and the inner cylinder is a screen with adjustable aperture. A rotating scraper assembly 52 is coaxially arranged inside the drum, and a high-frequency vibrator 53 is installed on the outer wall of the inner cylinder. A metering sensor is installed in the screw feeder 4. A labyrinth seal and a nitrogen curtain double sealing structure 54 are installed at both ends of the drum. The drum feeder 5 is installed between the screw feeder 4 and the inlet of the furnace 7 to solve the above problems. The scope of modification to the entire system is small, making it suitable for circulating fluidized bed boiler systems under construction, in operation, and newly built using biomass fuel. Multiple infrared moisture detection modules are installed in the screw feeder 4 for real-time monitoring of material moisture.

[0027] A buffer chamber is set between the inlet of the roller feeder 5 and the outlet of the screw feeder 4. A rotary feed valve is set at the inlet of the buffer chamber. When the material moisture content is detected to exceed the preset value, the material is temporarily conveyed to the buffer chamber. When the subsequent material moisture content is qualified, the material continues to be fed to the roller feeder 5, reducing the time of stopping the feeding.

[0028] The infrared moisture detection modules are all connected to the input terminal of the control system, and the high-frequency vibrator 53 is connected to the output terminal of the control system.

[0029] The infrared moisture detection module can be an infrared moisture meter, and both the high-frequency vibrator 53 and the infrared moisture detection module are commercially available products.

[0030] The rotary scraper assembly 52 is connected to a separate rotating motor and its rotation is controlled independently of that of the roller feeder 5.

[0031] like Figure 1 As shown in this embodiment, a biomass fuel drum feeder for a circulating fluidized bed boiler is implemented in the following way within the entire boiler system: Under the influence of gravity, the biomass fuel in silo 1 passes through the manual gate valve 2 and the rotary feeder valve 3 and then enters the screw feeder 4, and then the drum feeder 5 to achieve material dispersion and screening. Then, through the pipes and expansion joints 6 connected to the furnace 7, the fine particles are sent into the CFB boiler furnace 7 for combustion, while the coarse particles enter the crusher through the second outlet for crushing and recycling.

[0032] In this embodiment, large particles are defined as materials with a particle size of 2 mm or more, and fine particles are defined as materials with a particle size of no more than 2 mm. The rhomboid protrusions 51 are arranged in a spiral pattern.

[0033] The roller feeder 5 adopts a double-layer roller structure, such as Figure 2 As shown, the inner cylinder is made of wear-resistant steel plate 51 with diamond-shaped protrusions, and the outer cylinder is a screen structure with adjustable aperture, thereby achieving initial dispersion of materials. A rotating scraper assembly 52 is coaxially arranged inside the double-layer drum structure. The rotating scraper assembly 52 rotates in the opposite direction to the double-layer drum structure to forcibly break up agglomerates, and a high-frequency vibrator 53 is installed on the inner cylinder wall to prevent material adhesion.

[0034] The screw feeder 4 is equipped with an infrared moisture detection module and a material metering sensor. A buffer chamber is set between the inlet of the roller feeder 5 and the outlet of the screw feeder 4. The material metering sensor is used to assist in real-time feedback of material quantity.

[0035] A double-sealing structure of labyrinth seal and nitrogen curtain is installed at both ends of the drum to prevent boiler flue gas backflow. The feeding method is more than 30% more efficient than the traditional feeding method, and the blockage rate is reduced by 90%; the sealing system ensures an air leakage rate of less than 0.5%, improving boiler safety. Because no major modifications are required to the boiler body, the amount of modification work is small, the investment cost and maintenance workload are low, and it is economical.

[0036] The biomass fuel feeding device is attached to the circulating fluidized bed boiler system. Under the action of gravity, the biomass fuel in the silo 1 passes through the manual gate valve 2 and the rotary feed valve 3 and then enters the screw feeder 4, and then enters the drum feeder 5 to achieve material dispersion. Fine particles are fed into the CFB boiler furnace 7 for combustion through the pipe and expansion joint 6 connected to the furnace 7. Coarse particles enter the crusher through the second outlet for crushing and recycling. The bottom ash after combustion in the furnace 7 is cooled by the ash cooler 8 and discharged to the vibrating screen 9. After continuous screening by the vibrating screen, large particles larger than 2mm are sent to the ash conveyor belt 10 to be transported out of the boiler, while the fine particles 0-2mm after screening are collected and stored in the storage tank 11.

[0037] In summary, this application achieves material buffering and flow control through two-stage feeding. The screw feeder ensures initial sealing and conveying, while the roller feeder further screens and distributes the materials. This enables graded processing of biomass fuel, allowing fuel that meets particle size requirements to directly enter the furnace, while excessively large particles are returned to the crusher, thus improving combustion efficiency. The scraper prevents screen blockage, and the vibrator enhances screening efficiency, working together to ensure continuous material flow. The labyrinth seal and nitrogen curtain double seal prevent combustible gas backflow and oxygen entry, enhancing system safety.

[0038] The above content is only for illustrating the technical concept of this utility model and should not be construed as limiting the scope of protection of this utility model. Any modifications made to the technical solution based on the technical concept proposed in this utility model shall fall within the scope of protection of the claims of this utility model.

Claims

1. A feeding device suitable for a circulating fluidized bed boiler using biomass fuel, characterized in that, It includes a screw feeder (4) and a drum feeder (5). The inlet of the drum feeder (5) is connected to the outlet of the screw feeder (4). The drum feeder (5) is provided with a first outlet and a second outlet. The first outlet is connected to the furnace (7), and the second outlet is connected to the crusher. The drum feeder (5) includes an inner cylinder and an outer cylinder arranged coaxially. The inner wall of the outer cylinder is provided with diamond-shaped protrusions (51), and the inner cylinder is a screen with adjustable aperture. A rotating scraper group (52) is arranged coaxially with the inner cylinder, and a high-frequency vibrator (53) is provided on the outer wall of the inner cylinder. The two ends of the drum are provided with a labyrinth seal and a nitrogen curtain double seal structure (54).

2. The circulating fluidized bed boiler feeding device suitable for biomass fuel according to claim 1, characterized in that, It also includes a silo (1), and the outlet of the silo (1) is sequentially equipped with a manual gate valve (2), a rotary feeder valve (3) and a screw feeder (4) along the biomass fuel flow direction.

3. The circulating fluidized bed boiler feeding device suitable for biomass fuel according to claim 1, characterized in that, The height of the rhomboid protrusions is 10-30mm, they are arranged in a spiral array, and the spacing between the rhomboid protrusions is 5-15mm.

4. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 1, wherein An expansion joint (6) is provided between the outlet of the roller feeder (5) and the inlet of the furnace (7).

5. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 1, wherein The rotary scraper assembly (52) is connected to a separate rotary motor.

6. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 1, wherein The rhomboid protrusions (51) are arranged in a spiral pattern.

7. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 1, wherein The high-frequency vibrator (53) and the infrared moisture detection module are both connected to the input end of the control system, and the high-frequency vibrator (53) is connected to the output end of the control system.

8. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 1, wherein The screw feeder (4) is equipped with an infrared moisture detection module and a material metering sensor.

9. The biomass fuel feeding device for a circulating fluidized bed boiler according to claim 8, wherein A buffer chamber is provided between the inlet of the roller feeder (5) and the outlet of the screw feeder (4).

10. A circulating fluidized bed boiler system suitable for biomass fuel, characterized by The feeding device includes the circulating fluidized bed boiler feeding device suitable for biomass fuel as described in any one of claims 1-9.

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