Efficient hidden hood type air distribution device of circulating fluidized bed

Abstract

The invention discloses an efficient hidden air cap type circulating fluidized bed air distribution device which comprises an air chamber, a slag discharge pipe and a plurality of air caps, the top wall of the air chamber is a water-cooling air distribution plate, the air caps are arranged on the water-cooling air distribution plate, the slag discharge pipe is installed in the air chamber, the upper end of the slag discharge pipe is connected with the water-cooling air distribution plate, and the lower end of the slag discharge pipe extends out of the air chamber. The heights of the air caps are sequentially reduced from the edge of the hearth to the deslagging pipe and are arranged in a step shape, the fluidized bed surface is formed by laying wear-resistant castable, the fluidized bed surface is in a step shape corresponding to the air caps, the air caps are embedded in the wear-resistant castable, the whole fluidized bed surface is inclined from the edge of the hearth to the deslagging pipe, and the air cap head is arranged at the upper end of the air cap connecting pipe. A sealed inner cavity is formed in the air cap shell, the upper end of the air cap connecting pipe is communicated with the sealed inner cavity, the lower end of the air cap connecting pipe vertically penetrates through the water-cooling air distribution plate and then is communicated with the air chamber, and the labyrinth plate is located in the sealed inner cavity and divides the sealed inner cavity into a labyrinth type air channel. The continuous operation time of the boiler can be prolonged, and economic benefits are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of circulating fluidized bed boiler technology, and more specifically to a furnace air distribution device used in a circulating fluidized bed waste boiler. Background Technology

[0002] Currently, fluidized bed boilers (e.g., bubbling bed or circulating fluidized bed) mainly employ two types of air distribution devices: the air cap type and the perforated plate type. The perforated plate type is generally less common, while the air cap type is the most widely used in domestic fluidized bed boilers. The air cap type mainly consists of an air chamber, an air distribution plate, an air cap, and an insulation layer. Hot air entering the furnace passes through the equalizing air chamber into the fluidizing air cap, then through the air cap connector and the air cap head, and is injected at high speed into the furnace through small holes in the air cap, forming a uniform fluidizing air. This achieves the purpose of uniform fluidization of the furnace bed material and providing the primary air required for combustion.

[0003] Circulating fluidized bed incineration technology, as a highly efficient and clean combustion technology, has been increasingly widely used in waste treatment in recent years. However, due to the imperfect waste recycling system and the complex composition of waste, large non-combustible materials (such as stones and bricks) and metallic materials like wire inevitably enter the furnace. In particular, solid metal objects such as wire, aluminum cans, bottle caps, and iron blocks soften and are difficult to discharge from the ash discharge port, easily causing blockages. Therefore, the technical challenge in solid waste and garbage boilers lies in ensuring smooth fluidization of the fluidized bed while simultaneously solving the ash discharge problem.

[0004] Traditionally, the bed surface of the furnace air distribution plate was mainly flat, with a slag discharge port in the middle. It had the advantages of simple structure and was widely used in circulating fluidized bed boilers. The fluidizing air caps were mainly mushroom head type and bell type; the mushroom head type adopted an integral structure design, while the bell type relied on the weight of the air cap head itself to rest on the castable bed surface. When circulating fluidized bed technology is applied to waste treatment, the shortcomings of the horizontally arranged bed surface become apparent: due to the complex composition of waste and the large differences in particle size and density of the bed material, the existing planar furnace bed structure has gaps between the air caps on the bed surface. During boiler operation, heavy metals, stones, etc., accumulate in these gaps, and the air cap heads are easily entangled by wires and other debris. After long-term boiler operation, the air cap holes are easily blocked. Some large and heavy particles are deposited on the bed surface or accumulate around the ash discharge port. After being blown by the fluidizing air, they continue to accumulate around, forming increasingly larger fluidization dead zones, affecting the fluidization effect of the entire bed surface, greatly reducing the uniformity and stability of the flow in the bed, and even causing a non-fluidized state at the bottom. This can easily lead to ash discharge port blockage and coking and slagging in the furnace, thus forcing the boiler to shut down and shortening the continuous operating time of the boiler. Especially when there is slag buildup above the air vent of the vent cap, the air blown out of the vent is blocked by the slag and can only flow downwards. At this time, the vent cap is subjected to the buoyancy of the upward wind and can be easily blown off, causing the boiler to malfunction.

[0005] Therefore, the arrangement of air caps is a key factor in the uniform air distribution of a circulating fluidized bed, directly determining the fluidization effect and affecting boiler combustion. Currently, in operating circulating fluidized bed boilers, the air caps are all arranged above the bed surface, protruding approximately 100mm-200mm. During boiler operation, because the air caps are exposed above the bed surface, they are subjected to a large amount of circulating material and bottom ash scouring, resulting in wear. In severe cases, this can cause localized perforation, coking, and forced boiler shutdown, shortening the boiler's operating cycle. This not only increases boiler operating costs but also seriously affects the safety and efficiency of boiler operation. Furthermore, due to the presence of circulating ash adhering to the wall, the boiler... The ash flow around the furnace is large. If the air cap is too close to the surrounding bed surface, it can easily damage the castable. If it is too far away, there will be fluidization dead corners around the bed surface, resulting in uneven fluidization. Furthermore, since there are non-combustible foreign objects in the fuel, especially iron blocks and wires contained in garbage, biomass, and industrial solid waste, these foreign objects will be blocked by the air caps that are higher than the bed surface as they move towards the ash discharge port. This will cause them to wrap around the air caps or get stuck in the gaps of the air caps. Over time, this will cause the air caps to become blocked, resulting in poor fluidization and forcing the boiler to shut down. Summary of the Invention

[0006] The purpose of this invention is to provide a highly efficient concealed wind cap type circulating fluidized bed air distribution device to solve the problem of poor fluidization in existing circulating fluidized bed boilers when burning fuels containing a lot of impurities such as biomass and waste, which leads to coking and slagging on the bed surface and forces the boiler to shut down. This greatly increases the continuous operating time of the boiler and significantly improves economic efficiency.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention discloses a highly efficient concealed vented circulating fluidized bed air distribution device, comprising an air chamber, a slag discharge pipe, and several vents. The top wall of the air chamber is a water-cooled air distribution plate, and the several vents are disposed on the water-cooled air distribution plate. The slag discharge pipe is installed in the air chamber and its upper end is connected to the water-cooled air distribution plate, while its lower end extends out of the air chamber. The several vents are arranged in a stepped shape, with the height decreasing sequentially from the furnace edge to the slag discharge pipe. The fluidized bed surface is constructed of wear-resistant castable, and the fluidized bed surface is stepped, corresponding to the vents. The vents are embedded in the wear-resistant castable. The fluidized bed surface is inclined from the furnace edge towards the slag discharge pipe. Each vent includes a vent head and a vent connector, with the vent head disposed on the vent connector. At its upper end, the hood head is flat and includes a hood shell and a labyrinth plate. The hood shell is a rectangular cylinder with an opening at the lower end. A sealing plate is connected to the opening end of the hood shell to form a sealed inner cavity. The upper end of the hood connector passes through the sealing plate and communicates with the sealed inner cavity. The lower end of the hood connector passes vertically through the water-cooled air distribution plate and communicates with the air chamber. The lower part of the hood shell facing the slag discharge pipe has at least two air outlets. The labyrinth plate is located in the sealed inner cavity and divides the sealed inner cavity into a labyrinth-type air channel. The hood connector is connected to one end of the labyrinth-type air channel, and the air outlets are connected to the other end of the labyrinth-type air channel.

[0008] By adopting the above technical solution, the air cap is embedded in the castable refractory, and the circulating ash washes over the castable refractory, which solves the problem of air cap wear and greatly extends the air cap replacement cycle from about 10% per year to 10% every 5 years. The air caps embedded in the castable refractory around the boiler furnace also solve the problem of uneven fluidization around the perimeter. At the same time, an air outlet is set only on the lower part of the side of the air cap shell facing the slag discharge pipe. When the air cap is arranged on the air distribution plate, the air outlet faces the direction of the slag discharge pipe to facilitate boiler slag discharge. The unidirectional air outlet can cause the fluidized bed bottom material to flow in a directional manner. The airflow formed at the bottom of the furnace can blow coarse bed material towards the slag discharge port and blow large non-combustible materials in the designed direction, which is conducive to the flow of large ash particles to the slag discharge port and their smooth discharge, so as not to affect the normal operation of the boiler. It can also make the turbulence in the furnace more intense, which is conducive to the combustion of waste.

[0009] Furthermore, the height difference between two adjacent rows of wind caps is arranged in an arithmetic progression.

[0010] By adopting the above technical solution, after the height difference between adjacent front and rear rows of air caps, the fluidizing air ejected from the rear row of air caps directly enters the furnace, which can enhance the disturbance at the bottom of the bed and is conducive to particle mixing. When the air caps are arranged in a stepped manner, there is a height difference between adjacent front and rear rows of air caps, and the outer shell of the air caps is flat, which can reduce the height difference between the front and rear rows of air caps and reduce the problem of uneven air distribution caused by the height difference of the bed material.

[0011] Furthermore, the angle between the overall structure of the fluidized bed surface and the horizontal plane is 10°-30°.

[0012] By adopting the above technical solution, the high-speed air ejected from the rear air cap can blow over the top of the front air cap, which greatly improves the impact wear behind the air cap, and is conducive to improving the fluidization uniformity in the furnace and the operating cycle of the boiler. After the directional air caps are arranged in a stepped manner, the directional blowing ability is stronger, which is conducive to the discharge of large and heavy particles.

[0013] The fluidized bed surface is arranged inclined from the edge of the furnace towards the ash discharge pipe. The air cap head only has air outlets on the side facing the ash discharge pipe. When large pieces of non-combustible material fall onto the inclined bed surface, they will slowly move along the ash discharge port at the lower end of the inclined bed surface by their own gravity, the thrust of the fluidized bed material, and the blowing force of the unidirectional air from the air outlet of the air cap, and finally enter the ash discharge pipe. This smoothly discharges large pieces of non-combustible material and large pieces of ash, avoiding poor ash discharge and ensuring that no coking occurs at the ash discharge port. In particular, the use of a slag discharge pipe with an oval cross section is more conducive to the arrangement of the air cap and the discharge of ash than a circular slag discharge pipe. Without increasing the diameter of the ash discharge pipe, it solves the problem of ash discharge pipe blockage and bed surface coking and slagging caused by poor fluidization when burning fuels containing a lot of impurities such as biomass, garbage, and industrial solid waste in circulating fluidized bed boilers, which forces boiler shutdown due to poor fluidization.

[0014] Furthermore, each row of wind caps is embedded in the wear-resistant castable to form a small plane that is inclined towards the slag discharge pipe. The angle between the small plane and the horizontal plane is 5°-10°. Each small plane is combined in equal increments to form a stair-like stepped bed surface.

[0015] By adopting the above technical solution, after the air caps are arranged on the air distribution plate, the gap between adjacent air caps is small. The reserved expansion gap is filled with castable material, forming a small plane that is slightly inclined at 5°-10° towards the slag discharge pipe on the upper part of the air cap. The small plane is smooth without any protrusions or depressions, which is conducive to the flow of bed material. Multiple slightly inclined small planes are arranged in a stepped manner to form a bed surface structure with a larger inclination angle of 10°-30°. There are no fluidization dead corners on the entire bed surface, and there are no protrusions or depressions in any part. Under the combined action of the flat air cap shell, the blowing force of the air cap outlet in one direction, and the fluidized bed surface that is inclined towards the slag discharge pipe, when a large piece of non-combustible material falls onto the inclined bed surface, it can move smoothly along the inclined bed surface to the slag discharge port at the lower end without any obstruction, relying on its own gravity, the thrust of the fluidized bed material, and the blowing force of the air cap outlet in one direction, and finally enter the slag discharge pipe.

[0016] Furthermore, the axis of the air outlet is inclined downward along the air outlet direction, and the angle between the axis and the horizontal plane is 5°-10°.

[0017] By adopting the above technical solution, the spray direction of the air outlet is tilted downward, resulting in more uniform fluidization, reducing the possibility of coking, and avoiding wear caused by airflow blowing on adjacent air caps; at the same time, the downward tilting structure of the air outlet can also make the turbulence in the furnace more intense, which is conducive to the combustion of waste, and also prevents large particles such as coal gangue in the circulating fluidized bed boiler furnace from depositing on the bed surface, thereby ensuring stable fluidization quality in the furnace and normal operation of the boiler.

[0018] Furthermore, the total cross-sectional area of ​​the air outlet is smaller than the cross-sectional area of ​​the air inlet pipe.

[0019] By adopting the above technical solutions, the wind force blown out by the wind cap is stronger, making it easier to propel non-combustible materials in the designed direction. The resistance of the wind cap can be optimized by adjusting the number of air outlets.

[0020] Furthermore, the maze plate is inverted L-shaped and includes a horizontal plate and a vertical plate that are perpendicular to each other. The front end and rear end of the maze plate are connected to and sealed to the front and rear side walls of the hood shell, respectively. A first air duct is formed between the horizontal plate, the vertical plate and the sealing plate. A second air duct is formed between the horizontal plate and the left side wall of the hood shell. A third air duct is formed between the horizontal plate and the upper side wall of the hood shell. The lower end of the vertical plate abuts against and seals with the sealing plate. A fourth air duct is formed between the vertical plate and the right side wall of the hood shell. The first air duct, the second air duct, the third air duct and the fourth air duct are interconnected to form the maze-type air duct.

[0021] By adopting the above technical solution, the fluidizing air enters the inner cavity of the air cap through the air cap pipe from the air chamber. The flow direction changes from horizontal to left, vertical to upward, horizontal to right to vertical downward. Then it flows into the furnace at an angle through the air outlet. Because the airflow goes through multiple reversals and the air outlet is tilted downward, particles will not be deposited, and large particles are also difficult to leak back into the air chamber. Its labyrinth structure effectively avoids the occurrence of slag leakage.

[0022] Furthermore, the height of the air outlet is lower than the height of the horizontal plate.

[0023] By adopting the above technical solution, the height of the air outlet is set to be lower than the height of the horizontal plate, so that the vertical plate can further prevent the backflow of bed material and block the backflow of bed material, making it difficult for the material to flow back to the air chamber through the air outlet.

[0024] Furthermore, the vent cap connector extends upward to the horizontal plate and seals with the horizontal plate, and the upper side of the vent cap connector has several air inlets evenly distributed around the circumference.

[0025] By adopting the above technical solution, after the wind cap nozzle extends into the inner cavity of the wind cap shell, even if the bed material enters the inner cavity, it is not easy for it to enter the air chamber through the wind cap nozzle. Furthermore, the wind cap resistance can be optimized by adjusting the number of air inlets on the wind cap nozzle and air outlets on the wind cap shell.

[0026] Furthermore, the cross-section of the slag discharge pipe is oval.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are as follows: In actual operation, the high-efficiency concealed wind cap type circulating fluidized bed air distribution device of this invention allows boiler primary air to enter the furnace through the wind chamber and the wind cap on the air distribution plate, filling the furnace space with fluidized bed material. When biomass containing stones and metals, garbage, industrial solid waste, etc., fall into the furnace for combustion, the fine particulate non-combustible materials in them are fluidized along with the bed material. Under the combined action of three factors—the flat wind cap shell, the unidirectional airflow from the wind cap outlet, and the fluidized bed surface inclined towards the slag discharge pipe—when large pieces of non-combustible material fall onto the inclined bed surface, they rely on their own gravity, the thrust of the fluidized bed material, and the unidirectional airflow from the wind cap outlet. It will slowly move along the inclined bed surface to the slag discharge port at the lower end, and finally enter the slag discharge port to smoothly discharge large pieces of non-combustible materials and large pieces of ash and slag, avoiding poor slag discharge and ensuring that no coking occurs at the slag discharge port. In particular, the use of a slag discharge pipe with an oval cross section is more conducive to the arrangement of the air cap and the discharge of ash and slag than a circular slag discharge pipe. Without increasing the diameter of the slag discharge pipe, it solves the problem of poor fluidization in circulating fluidized bed boilers when burning fuels containing a lot of impurities such as biomass, garbage, and industrial solid waste, which leads to slag blockage of the slag discharge pipe and coking and slag on the bed surface, forcing the boiler to shut down. This greatly extends the continuous operation time of the boiler. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a cross-sectional schematic diagram of the bed surface structure in the high-efficiency concealed hood type circulating fluidized bed air distribution device according to Embodiment 1 of the present invention; Figure 2 This is a top view schematic diagram of the bed surface structure (the air cap is set on the water-cooled air distribution plate and the fluidized bed surface is not covered with wear-resistant castable material) in the efficient concealed air cap type circulating fluidized bed air distribution device of Embodiment 1 of the present invention. Figure 3This is a top view schematic diagram of the bed surface structure (the air cap is set on the water-cooled air distribution plate and the fluidized bed surface is built with wear-resistant castable) in the efficient concealed air cap type circulating fluidized bed air distribution device of Embodiment 1 of the present invention. Figure 4 , Figure 5 for Figure 1 A partially enlarged schematic diagram of the efficient concealed hood type circulating fluidized bed air distribution device of Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the structure of the wind cap in the high-efficiency concealed wind cap type circulating fluidized bed air distribution device according to Embodiment 1 of the present invention; Figure 7 This is a front sectional view of the vent in the high-efficiency concealed vent type circulating fluidized bed air distribution device according to Embodiment 1 of the present invention; Figure 8 for Figure 7 Schematic diagram of the cross section at point AA; Figure 9 This is a left-side cross-sectional view of the air hood in the efficient concealed air hood type circulating fluidized bed air distribution device according to Embodiment 1 of the present invention; Figure 10 This is a right-side schematic diagram of the air hood in the high-efficiency concealed air hood type circulating fluidized bed air distribution device according to Embodiment 1 of the present invention; Figure 11 This is a schematic diagram of the structure of the wind cap in the high-efficiency concealed wind cap type circulating fluidized bed air distribution device of Embodiment 2 of the present invention.

[0030] Explanation of reference numerals in the attached drawings: 1. Vent head; 11. Sealing plate; 12. Air outlet; 13. Vent outer shell; 14. Labyrinth plate; 141. Horizontal plate; 142. Vertical plate; 15. First air duct; 16. Second air duct; 17. Third air duct; 18. Fourth air duct; 2. Vent connector; 21. Air inlet; 3. Air chamber; 4. Slag discharge pipe; 5. Wear-resistant castable; 6. Water-cooled air distribution plate. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of this invention, it should be understood that the terms "length," "width," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] Example 1 like Figures 1 to 10 As shown, the efficient concealed wind cap type circulating fluidized bed air distribution device of Embodiment 1 of the present invention includes an air chamber 3 surrounded by a water-cooled wall, a water-cooled air distribution plate 6, a slag discharge pipe 4, and several wind caps disposed on the water-cooled air distribution plate 6. The top wall of the air chamber 3 is the water-cooled air distribution plate 6. The slag discharge pipe 4 is installed in the air chamber. The upper end of the slag discharge pipe 4 is connected to the water-cooled air distribution plate 6. The lower end of the slag discharge pipe 4 extends out of the air chamber 3 and is connected to a slag discharge valve and a slag cooler. Preferably, the cross-section of the slag discharge pipe is oval.

[0036] Specifically, the air cap includes an air cap head 1 and an air cap connecting pipe 2. The air cap head 1 is located at the upper end of the air cap connecting pipe 2, and the lower end of the air cap connecting pipe 2 is vertically installed on the water-cooled air distribution plate 6 and connected to the air chamber 3. The air cap connecting pipe 2 and the water-cooled air distribution plate 6 are fixed by welding or other methods. The air caps are arranged in rows from the edge of the furnace to the upper opening of the slag discharge pipe 4, with the height decreasing sequentially in a stepped arrangement. The height difference between two adjacent rows of air caps is equal, and the height difference is determined by the length of the air cap connecting pipe 2.

[0037] Furthermore, corresponding to the air cap, the fluidized bed surface is also stepped. The fluidized bed surface is constructed of wear-resistant castable. The wear-resistant castable covers the area between the air distribution plate 6 and the upper edge of the air cap. Except for the air outlet 12, the entire air cap is embedded in the wear-resistant castable, so that the fluidized bed surface is inclined from the edge of the furnace to the upper opening of the slag discharge pipe 4 and is arranged in a stepped shape. The angle α between the overall structure of the fluidized bed surface and the horizontal plane is 10°-30°.

[0038] In this first embodiment, the air cap head is a rectangular structure, with a horizontal dimension of 140mm × 140mm that is 50mm larger than the vertical dimension. Each row of air caps is embedded in the castable to form a small plane inclined towards the slag discharge pipe, with an angle β of 5° between the small plane and the horizontal plane. Each small plane is arranged in an arithmetic sequence to form a stair-like stepped bed surface. The distance between two adjacent air caps in each row is 160mm, the distance between two adjacent rows of air caps is 160mm, the height difference is 60mm, and the overall structure of the fluidized bed surface has an angle of 20° with the horizontal plane.

[0039] Specifically, the hood head includes a hood shell 13 and a labyrinth plate 14. The hood shell 13 is a rectangular cylinder with an opening at the bottom. The lower part of the right side wall of the hood shell 13 is provided with 7 air outlet holes 12. In this embodiment, the air outlet holes 12 are a single row of circular holes. This form makes the air distribution of the hood more uniform, and the design of the single row of circular openings also strengthens the rigidity of the outlet air. The axis of the air outlet holes 12 is inclined downward along the air outlet direction, and the angle between its axis and the horizontal plane is 5°. The opening end of the hood shell 13 is connected to a sealing plate 11, so that the hood shell 13 forms a sealed inner cavity. The labyrinth plate 14 is located in the inner cavity. The dimension of the hood shell 13 in the horizontal direction is larger than the dimension in the vertical direction.

[0040] Preferably, the maze plate 14 is inverted L-shaped and consists of a horizontal plate 141 and a vertical plate 142 that are perpendicular to each other. The width of the horizontal plate 141 in the left-right direction is greater than the height of the vertical plate 142. The front end and rear end of the maze plate 14 are connected to and sealed to the front and rear side walls of the hood shell 13, respectively. A first air duct 15 is formed between the horizontal plate 141, the vertical plate 142 and the sealing plate 11. A second air duct 16 and a third air duct 17 are formed between the horizontal plate 141 and the left and upper side walls of the hood shell 13, respectively. The vertical plate 142 is close to the right side wall of the hood shell 13 and its lower end abuts against and seals the sealing plate 11. A fourth air duct 18 is formed between the vertical plate 142 and the right side wall. The first air duct 15, the second air duct 16, the third air duct 17 and the fourth air duct 18 are interconnected to form a maze-type air duct. At this time, the upper end of the hood connector 2 passes through the sealing plate 11 and is connected to the first air duct 15, and the lower end of the hood connector 2 passes through the air distribution plate and is connected to the air chamber. The labyrinth plate 14 divides the inner cavity of the hood shell into a labyrinth-style air duct. The hood connector 2 is connected to the first air duct 15, and the air outlet 12 is connected to the fourth air duct 18.

[0041] In this first embodiment, the height of the air outlet 12 is lower than the height of the horizontal plate 141, and the total cross-sectional area of ​​the air outlet 12 is smaller than the cross-sectional area of ​​the air inlet pipe.

[0042] The working principle of the high-efficiency concealed hood type circulating fluidized bed air distribution device in this embodiment is as follows: When the air cap is arranged on the air distribution plate, the air outlet 12 faces the slag discharge pipe. When the boiler is running normally, the primary air flows upward from the air chamber through the lower end of the air cap pipe 2. It first enters the inner cavity of the air cap, and then the flow direction changes from horizontal to left, vertical upward, horizontal to right to vertical downward. After that, it flows into the furnace at an angle through the air outlet 12. Since the air outlet 12 is only set on the lower part of the right side wall of the air cap shell 13, the air outlet 12 in one direction can make the fluidized bed bottom material flow in a directional manner. Under the combined action of the flat air cap shell, the blowing force of the air outlet of the air cap in one direction, and the fluidized bed surface arranged at an angle towards the slag discharge pipe, when a large piece of non-combustible material falls onto the inclined bed surface, it will slowly move along the slag outlet at the lower end of the inclined bed surface by relying on its own gravity, the thrust of the fluidized bed material, and the blowing force of the air outlet of the air cap in one direction, and finally enter the oval slag discharge pipe, so as to smoothly discharge the large piece of non-combustible material and large piece of ash. When the water content in the fuel suddenly changes, causing a sharp fluctuation in the pressure inside the furnace, or when the fan surges or the boiler load changes, causing a decrease in flue gas pressure and flow, resulting in backflow of flue gas, the design of the labyrinth-type air duct and the blocking of the vertical plate 142 of the labyrinth plate 4 can effectively prevent the bed material, which is a solid particle, from flowing back into the return air chamber.

[0043] Example 2 like Figure 11 As shown, the difference between the high-efficiency concealed hood type circulating fluidized bed air distribution device in Embodiment 2 and Embodiment 1 is that the hood pipe 2 extends upward to the horizontal plate 141 and is sealed with the horizontal plate 141, and the upper side of the hood pipe 2 is provided with a plurality of air inlet holes 21 evenly distributed along its circumference.

[0044] In this second embodiment, after the wind cap pipe 2 extends into the inner cavity of the wind cap shell 13, even if the bed material enters the inner cavity, it is not easy to enter the air chamber through the wind cap pipe 2. The wind cap resistance can also be optimized by adjusting the number of air inlet holes 21 on the wind cap pipe 2 and air outlet holes 12 on the wind cap shell 13.

[0045] The working principle of the high-efficiency concealed hood type circulating fluidized bed air distribution device in this embodiment is as follows: When the air cap is arranged on the air distribution plate, the air outlet 12 faces the slag discharge pipe. When the boiler is running normally, the primary air flows upward from the air chamber through the lower end of the air cap connecting pipe 2, rises to its top, and is evenly sprayed out through the air inlet 21 around the air cap connecting pipe 2, entering the inner cavity of the air cap. Then the flow direction changes from horizontal to left, vertical to upward, horizontal to right to vertical to downward, and then flows into the furnace at an angle through the air outlet 12. Since the air outlet 12 is only set on the lower part of the right side wall of the air cap shell 13, it is a single-direction airflow. The air outlet 12 enables the fluidized bed material to flow in a directional manner. Under the combined effect of three factors—the flat air cap shell, the unidirectional airflow from the air cap outlet, and the fluidized bed surface inclined towards the slag discharge pipe—when large pieces of non-combustible material fall onto the inclined bed surface, they will slowly move along the slag discharge port at the lower end of the inclined bed surface due to their own gravity, the thrust of the fluidized bed material, and the unidirectional airflow from the air cap outlet, eventually entering the oval slag discharge pipe, thus smoothly discharging the large pieces of non-combustible material and ash. When the water content in the fuel suddenly changes, causing a sharp fluctuation in the furnace pressure, or when the fan surges or the boiler load changes, causing a decrease in flue gas pressure and flow, resulting in flue gas backflow, the labyrinthine duct design and the blocking effect of the vertical plate 142 of the labyrinth plate 14 can effectively prevent the bed material, as solid particles, from flowing back into the air chamber. The structural design of the air cap pipe 2 extending upward to the horizontal plate 141 can further prevent the bed material from flowing back into the air chamber.

[0046] Example 3 The difference between the high-efficiency concealed vent type circulating fluidized bed air distribution device in Embodiment 3 and Embodiment 1 is that the vent head is a rectangular structure, with a horizontal dimension of 140mm × 140mm that is 50mm larger than the vertical dimension. Each row of vents is embedded in the castable to form a small plane inclined towards the slag discharge pipe, with an angle β of 10° between the small plane and the horizontal plane. Each small plane is arranged in an arithmetic sequence to form a stair-like stepped bed surface. The distance between two adjacent vents in each row is 160mm, the distance between two adjacent rows of vents is 160mm, the height difference is 92mm, and the overall structure of the fluidized bed surface has an angle of 30° with the horizontal plane.

[0047] Example 4 The difference between the high-efficiency concealed vent type circulating fluidized bed air distribution device in Embodiment 4 and Embodiment 1 is that the vent head is a rectangular structure, with a horizontal dimension of 140mm × 140mm that is 50mm larger than the vertical dimension. Each row of vents is embedded in the castable to form a small plane inclined towards the slag discharge pipe, with an angle β of 8° between the small plane and the horizontal plane. Each small plane is arranged in an arithmetic sequence to form a stair-like stepped bed surface. The distance between two adjacent vents in each row is 160mm, the distance between two adjacent rows of vents is 340mm, the height difference is 60mm, and the overall structure of the fluidized bed surface has an angle of 10° with the horizontal plane.

[0048] The efficient concealed wind cap type circulating fluidized bed air distribution device of the present invention solves the problem of poor fluidization in circulating fluidized bed boilers when burning fuels containing a lot of impurities such as biomass, garbage, and industrial solid waste, which leads to slag discharge pipe blockage and coking and slagging on the bed surface, thus forcing the boiler to shut down. It greatly increases the continuous operation time of the boiler and significantly improves economic efficiency.

[0049] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-efficiency concealed hood type circulating fluidized bed air distribution device, characterized in that, The system includes a wind chamber, a slag discharge pipe, and several wind caps. The top wall of the wind chamber is a water-cooled air distribution plate, and the wind caps are disposed on the water-cooled air distribution plate. The slag discharge pipe is installed in the wind chamber and its upper end is connected to the water-cooled air distribution plate, while its lower end extends out of the wind chamber. The wind caps are arranged in a stepped shape, with the height decreasing sequentially from the edge of the furnace to the slag discharge pipe. The fluidized bed surface is constructed of wear-resistant castable, and the fluidized bed surface is stepped, corresponding to the wind caps. The wind caps are embedded in the wear-resistant castable. The fluidized bed surface is inclined from the edge of the furnace towards the slag discharge pipe. Each wind cap includes a cap head and a cap connector. The cap head is disposed at the upper end of the cap connector and is flat. The wind cap head includes a wind cap shell and a labyrinth plate. The wind cap shell is a rectangular cylinder with an opening at the bottom. A sealing plate is connected to the opening end of the wind cap shell to form a sealed inner cavity. The upper end of the wind cap connecting pipe passes through the sealing plate and communicates with the sealed inner cavity. The lower end of the wind cap connecting pipe passes vertically through the water-cooled air distribution plate and communicates with the air chamber. The lower part of the side of the wind cap shell facing the slag discharge pipe has at least two air outlets. The labyrinth plate is located in the sealed inner cavity and divides the sealed inner cavity into a labyrinth-shaped air channel. The wind cap connecting pipe is connected to one end of the labyrinth-shaped air channel, and the air outlets are connected to the other end of the labyrinth-shaped air channel.

2. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 1, characterized in that, The height difference between two adjacent rows of wind caps is arranged in an arithmetic progression.

3. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 1, characterized in that, The angle between the overall structure of the fluidized bed surface and the horizontal plane is 10°-30°.

4. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 1, characterized in that, Each row of wind caps is embedded in the wear-resistant castable to form a small plane that is inclined towards the slag discharge pipe. The angle between the small plane and the horizontal plane is 5°-10°. Each small plane is combined in equal increments to form a stair-like stepped bed surface.

5. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 1, characterized in that, The axis of the air outlet is inclined downward along the air outlet direction, and the angle between the axis and the horizontal plane is 5°-10°.

6. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 5, characterized in that, The total cross-sectional area of ​​the air outlet is smaller than the cross-sectional area of ​​the air inlet pipe.

7. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 1, characterized in that, The maze plate is inverted L-shaped and includes a horizontal plate and a vertical plate that are perpendicular to each other. The front end and rear end of the maze plate are connected to and sealed to the front and rear side walls of the hood shell, respectively. A first air duct is formed between the horizontal plate, the vertical plate and the sealing plate. A second air duct is formed between the horizontal plate and the left side wall of the hood shell. A third air duct is formed between the horizontal plate and the upper side wall of the hood shell. The lower end of the vertical plate abuts against and seals with the sealing plate. A fourth air duct is formed between the vertical plate and the right side wall of the hood shell. The first air duct, the second air duct, the third air duct and the fourth air duct are interconnected to form the maze-type air duct.

8. The high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 7, characterized in that, The height of the air outlet is lower than the height of the horizontal plate.

9. A high-efficiency concealed hood type circulating fluidized bed air distribution device according to claim 7, characterized in that, The vent tube extends upward to the horizontal plate and is sealed to the horizontal plate. The upper side of the vent tube has several air inlets evenly distributed around the circumference.

10. A high-efficiency concealed hood type circulating fluidized bed air distribution device according to any one of claims 1-9, characterized in that, The cross-section of the slag discharge pipe is oval.

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