Blowback type internal circulating fluidized bed boiler device

Abstract

The utility model discloses a back flushing type internal circulating fluidized bed boiler device which solves the technical problems that an air cap in an existing circulating fluidized bed boiler is complex in structure, easy to block and difficult to maintain. The boiler comprises a hearth and a spiral feeder, the hearth comprises a hearth upper part, a hearth middle part, a boiling layer and a hearth bottom part, a primary air pipe and a secondary air pipe which are coaxially arranged are arranged in the hearth, the primary air pipe is arranged in the secondary air pipe, and an annular secondary air channel is formed between the primary air pipe and the secondary air pipe; the secondary air nozzle is used for downwards spraying secondary air to supplement oxygen required by combustion and enhance airflow disturbance; an inlet of the spiral feeder is connected with the hopper, an outlet of the spiral feeder is connected with the primary air pipe, and fuel is fed into the primary air pipe through the spiral feeder, flows downwards along a pipeline and is sprayed out of an opening of the primary air pipe to enter the bottom of the hearth. According to the utility model, the primary air pipe and the secondary air pipe which are coaxial are used for replacing the traditional air distribution plate and air cap structure, so that the processing procedures and the material consumption are greatly reduced.

Description

Technical Field

[0001] This utility model relates to a reverse-flush internal circulation fluidized bed boiler device, specifically a reverse-flush internal circulation fluidized bed boiler device. Background Technology

[0002] Circulating fluidized bed (CFB) boiler technology has been widely used in my country due to its advantages such as high-efficiency combustion and wide fuel adaptability. As of 2017, my country had more than 3,000 CFB boilers in operation, with a total installed capacity of nearly 100 million kilowatts, accounting for 60% of the global total, making China the country with the largest number and scale of CFB boilers in the world. Existing CFB boilers generally use air distributors and air caps to achieve fluidized combustion. Taking a 10-15 t / h boiler as an example, 1,000-1,200 air caps need to be installed on the air distributor, each with 5-8 air holes, for a total of 5,000-10,000 air holes. Air is ejected through the air holes at a high speed of 30-50 m / s, driving the bed material to form a fluidized state.

[0003] Although the air distribution plate and air cap technology has matured since its development in the 1960s, its inherent defects still restrict the operating efficiency and reliability of boilers. First, the large number of air caps and the complex manufacturing process significantly increase the production cost of the air distribution plates. Second, during long-term operation, the air caps are prone to blockage by fuel ash or coking deposits, causing uneven fluidization, localized channeling or dead zones, and severely affecting combustion stability. Furthermore, severely worn air caps require frequent replacement, necessitating maintenance personnel to enter the furnace for cleaning or repair, resulting in a harsh working environment and low efficiency. These problems not only increase equipment maintenance costs but also reduce the boiler's operating cycle and reliability, especially for boilers burning biomass (such as corn stalks, rice husks, etc.) or low-calorific-value coal.

[0004] Therefore, there is an urgent need for a new type of fluidized bed boiler structure to simplify the fluidization device, reduce manufacturing costs, and reduce the difficulty of operation and maintenance, while improving fluidization uniformity and combustion efficiency, so as to meet the demand for efficient and clean utilization of low-calorific-value fuels such as biomass. Utility Model Content

[0005] The purpose of this invention is to provide a reverse-flush internal circulating fluidized bed boiler device to solve the technical problems of complex air cap structure, easy clogging, and difficult maintenance in existing circulating fluidized bed boilers. The boiler capacity applicable to this invention is suitable for small biomass fluidized bed boilers with a capacity of 6-75 t / h, and can also be used in coal-fired industrial boilers with a capacity of 10-140 t / h.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This utility model provides a reverse-fluidized internal circulating fluidized bed boiler device, including a furnace and a screw feeder. The furnace has a cylindrical structure, including an upper part, a middle part, a fluidized bed, and a bottom part from top to bottom. A primary air duct and a secondary air duct are provided inside the furnace. The primary air duct and the secondary air duct are composed of two coaxial pipes. The primary air duct is located inside the secondary air duct, forming an annular secondary air channel between them for downward injection of secondary air to supplement the oxygen required for combustion and enhance airflow turbulence. The screw feeder... The inlet is connected to the hopper, and the outlet is connected to the primary air duct. The primary air duct at the interface is tapered, and the air velocity increases and the dynamic pressure increases at its throat, forming a local negative pressure. The air inside the duct will not leak out through the inlet. At the same time, the material at the inlet is fed into the duct by the combined action of the negative pressure and the screw feeder, and is sent downward into the bottom of the furnace with the airflow. The bottom of the furnace is composed of an annular channel with a semi-circular cross section and a conical blunt body. Several ash holes and slag discharge pipes are evenly arranged along the circumference of the bottom. The fuel forms a vortex-like fluidized motion at the bottom of the furnace.

[0008] Furthermore, the concentric structure of the primary air duct and the secondary air duct is welded and fixed by several first fixed supports made of high-temperature resistant steel to maintain coaxiality; the secondary air duct is fixedly connected to the inner wall of the furnace by a second fixed support.

[0009] Furthermore, the outlet of the secondary air duct is located in the middle of the furnace, and its spray direction is vertically downward, which facilitates the mixing of particles entering the middle of the furnace with oxygen in the secondary air for continued combustion and burnout.

[0010] Furthermore, it also includes a flue gas outlet pipe, which is located in the upper part of the furnace. After the fuel in the upper part of the furnace is burned out, the resulting fly ash flows out of the furnace through the flue gas outlet pipe. The boiler outlet is connected to the flue, and the flue is equipped with an evaporative heating surface and a superheater to absorb the heat of the flue gas.

[0011] Furthermore, the furnace is surrounded by furnace walls with water-cooled wall tubes, which absorb heat during combustion to generate hot water or steam.

[0012] Furthermore, four ash collection holes are evenly arranged around the bottom of the furnace, and each ash collection hole is connected to a corresponding ash discharge pipe for discharging the bottom ash produced by combustion.

[0013] Based on the above technical solution, the embodiments of this utility model can produce at least the following technical effects:

[0014] This invention replaces the traditional air distribution plate and air cap structure with coaxial primary and secondary air ducts. The core components require only two concentric steel pipes and a few fixing supports, significantly reducing processing steps and material consumption. Compared to the complex process of installing thousands of air caps and vents in traditional technologies, it significantly reduces manufacturing costs and assembly difficulty. The combination of a semi-circular annular channel and a conical blunt body at the bottom of the furnace, along with a high-speed primary air jet, creates an inward-outward vortex fluidization of the fuel, ensuring uniform particle distribution. The secondary air duct outlet sprays vertically downwards, enhancing airflow turbulence and supplementing oxygen, promoting secondary combustion of unburned particles, and improving combustion efficiency and burnout rate. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the reverse-flush internal circulation fluidized bed boiler device of this utility model;

[0017] Figure 2 This is a top view of the reverse-flush internal circulating fluidized bed boiler device of this utility model;

[0018] Figure 3 yes Figure 1 A schematic diagram of the AA cross-sectional structure.

[0019] In the above figures, the component names corresponding to the reference numerals are as follows:

[0020] 1-Hopper, 2-Screw feeder, 3-Flue gas outlet pipe, 4-Upper part of furnace, 5-Middle part of furnace, 6-Secondary air duct, 7-Primary air duct, 8-Boiled layer, 9-Bottom of furnace, 10-Conical blunt body, 11-Slag discharge pipe, 12-First fixed support, 13-Second fixed support. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, and not all of them. 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 scope of protection of the present utility model. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present utility model.

[0022] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0023] Example 1

[0024] like Figure 1 and Figure 2 As shown, the reverse-flush internal circulation fluidized bed boiler device provided by this utility model mainly includes a hopper 1, a screw feeder 2, a flue gas outlet pipe 3, a furnace (composed of an upper part of the furnace 4, a middle part of the furnace 5, a boiling layer 8 and a bottom part of the furnace 9), a primary air duct 7, a secondary air duct 6, a conical blunt body 10, a slag discharge pipe 11, a first fixed support 12, and a second fixed support 13.

[0025] The furnace is cylindrical in shape and consists of an upper part 4, a middle part 5, a fluidized bed 8, and a bottom part 9 from top to bottom. The furnace contains a primary air duct 7 and a secondary air duct 6, which are composed of two concentric pipes. The concentric pipes include an inner pipe and an outer pipe, with the outer pipe surrounding the inner pipe. The inner pipe is the primary air duct 7, forming a primary air channel that transports fuel into the furnace. A screw feeder 2 is connected to the inner pipe at the top of the boiler. The inlet of the screw feeder 2 is connected to the hopper 1, and the outlet is connected to the primary air duct 7. Fuel is fed into the inner pipe by the screw feeder 2, and the airflow carrying the fuel downwards along the pipe, exiting the inner pipe and entering the bottom of the fluidized bed furnace. The outer pipe is the secondary air duct 6, and the annular channel between the inner and outer pipes forms the secondary air channel. Air flows downwards through this channel and is injected into the furnace at the middle part 5, providing oxygen for fuel combustion.

[0026] The lower part of the furnace is the fluidized bed 8, and below the fluidized bed 8 is the furnace bottom 9, which is a combination of a semi-circular and a conical shape. The upper part of the fluidized bed 8 is composed of a cylindrical structure with a uniform cross-section and a hollow frustum structure with a tapered cross-section. The furnace bottom 9 is composed of an annular channel with a semi-circular cross-section and a conical blunt body 10. Fuel is carried by primary air and injected into the furnace bottom 9, radiating outwards from the axis along the surface of the conical blunt body 10 and the annular channel, forming a vortex moving from the inside out. Four ash collection holes are evenly arranged around the circumference at the bottom, and four ash discharge pipes 11 are installed accordingly. The bottom ash generated during combustion is discharged through the ash discharge pipes 11, ensuring the stability of the bed material quantity at the bottom of the furnace. The furnace bottom 9 realizes the vortex-like radial flow of materials. The fluidized bed region composed of the furnace bottom 9 and the cylindrical and hollow frustum structures plays the same role as the fluidized bed in a traditional fluidized bed, and is therefore also called the fluidized bed.

[0027] The furnace is surrounded by furnace walls with water-cooled tubes, which absorb heat during combustion to produce hot water or steam.

[0028] In this embodiment, a flue gas outlet pipe 3 is also included, which is located in the upper part 4 of the furnace. During combustion, larger particle sizes are fluidized under the action of vortex airflow at the bottom of the furnace, undergoing intense heat transfer and combustion oxidation reactions with the high-temperature flue gas and primary air. Some smaller particles are carried upward by the airflow into the middle of the furnace, where they mix with oxygen in the secondary air and continue to burn and burn out. The fly ash formed after the fuel in the upper part of the furnace burns out is carried out of the furnace by the flue gas. The boiler outlet can be equipped with a reasonable flue arrangement to absorb the heat of the flue gas from the evaporation heating surface and superheater.

[0029] In this embodiment, the screw feeder 2 passes through the secondary air duct 6 and connects to the primary air duct 7, inputting fuel into the primary air duct 7. The fuel inlet of the primary air duct 7 is tapered, and the air velocity at its throat increases, the dynamic pressure increases, and a local negative pressure is formed. The air inside the pipe will not leak out through the inlet. At the same time, the material at the inlet is entered into the pipe by the combined action of the negative pressure and the screw feeder 2, and is sent downward into the bottom 9 of the furnace with the airflow.

[0030] Example 2

[0031] The technical features in this embodiment are basically the same as those in Embodiment 1. The same technical features and solutions will not be repeated here. Only the differences between Embodiment 2 and Embodiment 1 will be described here.

[0032] In this embodiment, as Figure 3As shown, the primary air duct 7 and the secondary air duct 6 are concentric cylindrical structures. The inner and outer cylinders are welded together at certain intervals by several sections of high-temperature resistant steel first fixed brackets to fix their relative positions and maintain the concentric structure. The two concentric air duct sleeves can be fabricated in one piece and assembled on site. The secondary air duct can be supported and fixed to the surrounding furnace walls by 8-12 second fixed brackets 13.

[0033] In this embodiment, the sections of the primary air duct 7 and the secondary air duct 6 inside the furnace are located in the high-temperature combustion zone and the high-temperature flue gas zone, and are made of high-temperature resistant steel, while the sections outside the furnace are made of Q235 steel to reduce material costs.

[0034] The specific process for using this device is as follows:

[0035] After being processed into particles with a diameter of 0-15mm by a crusher, the fuel is stored in a hopper. A screw feeder quantitatively delivers the fuel to the primary air duct. The primary air duct is an inner tube through which a high-speed airflow is introduced, carrying the fuel particles downwards and spraying them into the bottom of the furnace through the nozzle. The bottom of the furnace is composed of a semi-circular annular channel and a conical blunt body. Here, the fuel is subjected to airflow to form a vortex fluidization motion from the inside out, ensuring that the fuel particles are evenly distributed in the fluidized bed and burn stably.

[0036] The secondary air duct is a ring-shaped channel that is installed outside the primary air duct. Its outlet is located in the middle of the furnace. The secondary air is injected vertically downward to supplement the oxygen required for combustion. It also promotes the full mixing of unburned particles and oxygen by enhancing the airflow disturbance. The secondary air flow rate can be adjusted according to the fuel type and combustion intensity to achieve efficient combustion.

[0037] Water-cooled wall tubes are arranged around the furnace walls to absorb the heat generated by combustion and produce hot water or steam. The upper part of the boiling layer is a hollow frustum structure with a gradually narrowing cross section, which is connected to the middle furnace. The flue gas carries fine particles upward to the upper part of the furnace, and after further combustion, it is discharged through the flue gas outlet pipe. The heat of fly ash can be recovered and utilized through the evaporation heating surface or superheater set in the flue.

[0038] Four ash collection holes are evenly arranged around the bottom of the furnace, each connected to a ash discharge pipe. The bottom ash produced during combustion is periodically discharged through the ash discharge pipe to maintain a stable bed material quantity. The concentric pipes are made of high-temperature resistant steel. The primary air duct and the secondary air duct are kept concentric by fixed supports. During maintenance, the pipes can be cleared from outside the furnace without entering the furnace, significantly reducing workload.

[0039] Conventional circulating fluidized beds primarily employ an air distribution plate + air cap technology. Air is ejected from the vents on the air caps, driving the solid bed material on the air distribution plate to fluidize. In terms of manufacturing, thousands of air caps need to be installed on the air distribution plate, each with 5-8 vents, requiring specialized machining and resulting in a large workload for assembly. This new invention uses a circular tube airflow reverse-fluidization device. Primary air carries solid fuel to form a jet at a certain velocity, which is injected into the bottom of the furnace to create a vortex, achieving the fluidization of the material. The core components that need to be machined—the concentric circular tubes inside the furnace and the corresponding fixed supports—are only two circular steel pipes of different diameters and a small number of fixed supports, resulting in a significantly smaller machining and assembly workload compared to the former.

[0040] In conventional circulating fluidized beds, if the air caps become clogged during operation, each air hole needs to be checked and cleared individually, residue inside the air caps needs to be cleaned, and severely worn air caps may even need to be replaced, resulting in a large workload for maintenance and repair. During maintenance and repair, workers often need to enter the furnace for cleaning, where accumulated material easily generates dust, leading to poor air quality and a harsh working environment. This utility model adopts a circular tube airflow reverse-fluidization device. In its design, the pipe sections inside the furnace can be made of wear-resistant and high-temperature-resistant steel of a certain thickness. The outlet size of the primary and secondary air inlets is larger than the air cap air holes of the conventional method, and the opening direction is vertically downward. The probability of material blockage is much lower than that of the conventional air distribution plate air cap. Even if material blockage occurs, workers can clear and clean it from outside the furnace through the furnace door after shutdown. The maintenance workload is much less than that of the conventional method, and the working environment is also significantly improved.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A reverse-flush internal circulating fluidized bed boiler device, comprising a furnace and a screw feeder (2), characterized in that: The furnace is a cylindrical structure, which includes, from top to bottom, the upper part (4), the middle part (5), the boiling layer (8) and the bottom part (9). The furnace is equipped with a primary air duct (7) and a secondary air duct (6). The primary air duct (7) and the secondary air duct (6) are composed of two coaxial pipes. The primary air duct (7) is located inside the secondary air duct (6). The primary air duct (7) and the secondary air duct (6) form an annular secondary air channel, which is used to spray secondary air downward to supplement the oxygen required for combustion and enhance airflow turbulence. The inlet of the screw feeder (2) is connected to the hopper (1), and the outlet is connected to the primary air duct (7). The screw feeder (2) feeds the fuel into the primary air duct (7). The airflow flowing into the primary air duct (7) carries the fuel downward along the pipe and sprays it out of the primary air duct (7) into the bottom of the furnace (9). The bottom of the furnace (9) is composed of an annular channel with a semi-circular cross section and a conical blunt body (10). Several ash holes and slag discharge pipes (11) are evenly arranged along the circumference of the bottom, and the fuel forms a vortex-like fluidized motion at the bottom of the furnace.

2. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, The concentric structure of the primary air duct (7) and the secondary air duct (6) is fixed by welding several first fixed supports (12) made of high temperature resistant steel to maintain coaxiality; the secondary air duct (6) is fixedly connected to the inner wall of the furnace by a second fixed support (13).

3. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, The outlet of the secondary air duct (6) is located in the middle of the furnace (5), and its spray direction is vertically downward, which facilitates the mixing of particles entering the middle of the furnace (5) with oxygen in the secondary air for continued combustion and burnout.

4. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, It also includes a flue gas outlet pipe (3), which is located in the upper part (4) of the furnace. After the fuel in the upper part of the furnace is burned out, fly ash is formed and flows out of the furnace from the flue gas outlet pipe (3). The boiler outlet is connected to the flue, and an evaporation heating surface and a superheater are set inside the flue to absorb the heat of the flue gas.

5. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, The furnace is surrounded by furnace walls with water-cooled wall tubes, which absorb heat during combustion to produce hot water or steam.

6. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, The bottom of the furnace (9) has four ash holes evenly arranged around the circumference, and each ash hole is connected to a slag discharge pipe (11) for discharging the bottom ash produced by combustion.

7. The reverse-flush internal circulating fluidized bed boiler device according to claim 1, characterized in that, The screw feeder (2) passes through the secondary air duct (6) and connects to the primary air duct (7) to input fuel into the primary air duct (7). The fuel inlet of the primary air duct (7) is set with a tapered throat structure to accelerate the airflow and form a local negative pressure. The fuel is sucked in through the local negative pressure and air leakage is prevented.

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