Coal mill air duct against air flow scouring

Abstract

The present application belongs to the technical field of coal mill pulverizing equipment, and particularly relates to an air flow scouring prevention air duct of a coal mill, which comprises an air duct body and a flow resistance component. The air duct body comprises an upper rectangular air duct, an upper rectangular elbow, a vertical rectangular air duct, a lower rectangular elbow and a lower rectangular air duct which are sequentially communicated. The flow resistance component comprises a vertical flow resistance ring arranged in the upper rectangular air duct and the lower rectangular air duct, and an inclined flow resistance ring and a curved flow resistance sheet arranged in the upper rectangular elbow and the lower rectangular elbow. The vertical flow resistance ring is used to form an air flow stagnation zone on the inner wall of the upper rectangular air duct and the lower rectangular air duct, so as to prevent the direct scouring of the dust-containing hot air on the inner wall of the air duct body. In addition, the inclined flow resistance ring and the curved flow resistance sheet are used in the upper rectangular elbow and the lower rectangular elbow in a form of mutual cooperation, so as to form a plurality of air flow stagnation zones which are in a grid shape as a whole on the first wall surface and the second wall surface, and the effect of preventing the air flow from scouring the inner wall of the air duct body under a complex flow field is achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of coal mill pulverizing equipment, specifically relating to a coal mill air duct designed to prevent airflow erosion. Background Technology

[0002] When the hot air entering the coal mill flows through the rotary air preheater, it inevitably mixes with some dust. As this dust-laden hot air flows through the duct, the dust, driven by the airflow, often causes strong erosion of the duct wall, sometimes even wearing it through. Since the flow area of ​​the coal mill duct is significantly smaller than that of the hot air header, the air velocity of the dust-laden hot air flowing through the coal mill duct increases significantly, resulting in widespread erosion of the inner wall of the coal mill duct.

[0003] Currently, the main solutions to the scouring problem in coal mill ducts are to apply ceramic or mortar to the inner wall of the duct. However, ceramics are not firmly adhered and are very easy to fall off, while mortar has a large mass, which increases the load on the duct and is also expensive. Therefore, designing a low-cost duct that effectively prevents airflow scouring is of great significance. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a coal mill air duct that prevents airflow erosion. A flow-limiting component is provided on the inner wall of each part of the air duct body, and the airflow stagnation zone is formed on the inner wall of the air duct body by the cooperation of the components in the flow-limiting component, so as to prevent the airflow from eroding the inner wall of the air duct.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A coal mill air duct designed to prevent airflow erosion is disposed between a hot air header and the coal mill body, for transferring hot air supplied by the hot air header to the coal mill body. The coal mill air duct comprises:

[0007] The air duct body includes an upper rectangular air duct, an upper rectangular elbow, a vertical rectangular air duct, a lower rectangular elbow, and a lower rectangular air duct arranged in sequence. One end of the upper rectangular air duct is connected to the hot air main pipe, and one end of the lower rectangular air duct is connected to the coal mill body. The hot air provided by the hot air main pipe enters the air duct body from the upper rectangular air duct and passes through the upper rectangular elbow, the vertical rectangular air duct, the lower rectangular elbow, and the lower rectangular air duct in sequence before finally reaching the coal mill body. The two ends of the upper rectangular elbow are at a 90° angle, and the two ends of the lower rectangular elbow are also at a 90° angle.

[0008] The flow obstruction assembly includes several vertical flow obstruction rings, which are parallel to each other and evenly distributed at equal intervals on the inner walls of the upper rectangular air duct and the lower rectangular air duct, and the vertical flow obstruction rings are perpendicular to the inner walls of the upper rectangular air duct and the lower rectangular air duct.

[0009] The flow-blocking assembly further includes several inclined flow-blocking rings and several curved flow-blocking plates disposed inside the upper rectangular elbow and the lower rectangular elbow, wherein:

[0010] Several inclined flow-blocking rings are configured into two groups, and each group of inclined flow-blocking rings is evenly arranged inside the upper and lower rectangular elbows with the apex of the bending angle of the upper and lower rectangular elbows as the axis, respectively, and the included angle between any two adjacent inclined flow-blocking rings is equal. The inner wall surfaces of the upper and lower rectangular elbows away from the apex of the bending angle are configured as the first wall surface and the second wall surface, respectively. Several curved flow-blocking plates are evenly arranged on the first and second wall surfaces of the upper and lower rectangular elbows with equal spacing, based on the extension direction coinciding with the flow direction of the hot air.

[0011] The upper rectangular elbow's body structure is configured as a first air inlet and a first air outlet according to the sequential flow path of the hot air. Among the several inclined flow-blocking rings located inside the upper rectangular elbow, some of the inclined flow-blocking rings located inside the first air outlet are at a 90° angle to the first wall surface at a position fixed to the first wall surface. The lower rectangular elbow's body structure is configured as a second air inlet and a second air outlet according to the sequential flow path of the hot air. Among the several inclined flow-blocking rings located inside the lower rectangular elbow, some of the inclined flow-blocking rings located inside the second air outlet are at a 90° angle to the second wall surface at a position fixed to the second wall surface.

[0012] Based on the flow direction of the hot air inside the upper and lower rectangular bends, the angle between the angles formed by the several inclined flow-blocking rings and the first and second walls in the windward direction is the windward angle β, where β ≤ 90°.

[0013] Preferably, in the flow-blocking assembly, the vertical flow-blocking ring and the inclined flow-blocking ring are both formed by four rectangular flow-blocking unit plates, and the four flow-blocking unit plates are welded and fixed to each other. The vertical flow-blocking ring, the inclined flow-blocking ring, and the curved flow-blocking plate are also welded and fixed to the inner wall of the air duct body.

[0014] Preferably, in the vertical flow-blocking ring and the inclined flow-blocking ring, the length of the flow-blocking unit plate matches the inner wall of the air duct body, the width of the flow-blocking unit plate is L1, and 20mm < L1 < 50mm, and the thickness of the flow-blocking unit plate is L2, and 4mm < L2 < 10mm.

[0015] Preferably, in the upper rectangular elbow and the lower rectangular elbow, the included angle between two adjacent inclined flow-blocking rings is α, and 20° < α < 40°.

[0016] Preferably, in the upper rectangular elbow and the lower rectangular elbow, the width of the bending baffle is L3, and 20mm < L3 < 50mm, and the thickness of the bending baffle is L4, and 4mm < L4 < 10mm.

[0017] Preferably, in the upper rectangular elbow and the lower rectangular elbow, the distance between two adjacent bending baffles is L5, and 200mm < L5 < 400mm.

[0018] Preferably, in the upper rectangular air duct and the lower rectangular air duct, the distance between two adjacent vertical flow-blocking rings is L6, and 200mm < L6 < 400mm.

[0019] Preferably, in the upper rectangular air duct and the lower rectangular air duct, an airflow stagnation zone is formed between two adjacent vertical flow obstruction rings.

[0020] Preferably, in the upper rectangular bend and the lower rectangular bend, each inclined flow-blocking ring is configured with a flow-blocking unit plate that is fixedly welded to the first wall and the second wall as a forming plate, and several forming plates and several curved flow-blocking plates intersect each other to form a grid-like number of airflow stagnation zones.

[0021] Preferably, in the flow-blocking assembly, the vertical flow-blocking ring, the inclined flow-blocking ring, and the curved flow-blocking plate are all made of carbon steel.

[0022] The beneficial effects of this invention are as follows:

[0023] In general, this invention sets several vertical flow-blocking rings on the inner walls of the upper and lower rectangular air ducts. Utilizing the properties of fluid mechanics, when hot air flows to the vertical flow-blocking rings, the airflow cannot continue to flow along the inner wall of the air duct body due to the obstruction of the vertical flow-blocking rings. As a result, the kinetic energy of the airflow is converted into potential energy, that is, the flow velocity decreases and the pressure increases. Therefore, an airflow stagnation zone is formed in the area between two adjacent vertical flow-blocking rings. Since the airflow stagnation zone has the high pressure characteristic of kinetic energy converted into potential energy, the airflow pressure outside the airflow stagnation zone is lower than the pressure inside the airflow stagnation zone. Therefore, the airflow outside the airflow stagnation zone cannot enter the airflow stagnation zone, and thus the dust carried by the airflow will not enter the stagnation zone, thus preventing erosion of the air duct wall.

[0024] Furthermore, since the flow field of hot air at the upper and lower rectangular bends is more complex and the turbulence is more intense, this invention, based on the combination of inclined flow-blocking rings and curved flow-blocking plates at the upper and lower rectangular bends, forms several airflow stagnation zones in a grid-like pattern on both the first and second wall surfaces. This achieves the effect of preventing airflow from scouring the inner wall of the duct body even under complex flow fields. In addition, this invention also limits the windward angle β formed by the inclined flow-blocking rings and the first and second wall surfaces to β≤90°. This setting is conducive to the formation of airflow stagnation zones at this location, enabling this device to achieve the overall effect of preventing airflow scouring while reducing costs. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a front view schematic diagram of the overall structure of the present invention;

[0027] Figure 2 This is a partial front view structural diagram of the upper rectangular elbow in this invention;

[0028] Figure 3 This is a three-dimensional structural diagram of the upper rectangular elbow in this invention;

[0029] Figure 4 This is a partial front view structural diagram of the lower rectangular elbow in this invention;

[0030] Figure 5 This is a three-dimensional structural diagram of the lower rectangular elbow in this invention;

[0031] Figure 6 This is a schematic diagram of the combined structure of the flow-blocking unit plate in this invention;

[0032] Figure 7 This is a schematic diagram illustrating the formation of the airflow stagnation zone in this invention;

[0033] Figure 8 This is a partial side view of the upper rectangular elbow structure in this invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The solution provided by this utility model will now be described in detail with reference to the accompanying drawings.

[0037] In this technical solution, such as Figure 1 As shown, a coal mill air duct designed to prevent airflow erosion is disposed between the hot air header 1 and the coal mill body 2, for transmitting the hot air provided by the hot air header 1 to the coal mill body 2. The coal mill air duct includes: an air duct body 3 and a flow obstruction component 4.

[0038] Specifically, the air duct body 3 includes an upper rectangular air duct 301, an upper rectangular elbow 302, a vertical rectangular air duct 303, a lower rectangular elbow 304, and a lower rectangular air duct 305, which are sequentially connected. The cross-sections of the upper rectangular air duct 301, upper rectangular elbow 302, vertical rectangular air duct 303, lower rectangular elbow 304, and lower rectangular air duct 305 are all rectangular. One end of the upper rectangular air duct 301 is connected to the hot air header 1, and one end of the lower rectangular air duct 305 is connected to the coal mill body 2. The hot air provided by the hot air header 1 enters the air duct body from the upper rectangular air duct 301 and then sequentially passes through the upper rectangular elbow 302, vertical rectangular air duct 303, lower rectangular elbow 304, and lower rectangular air duct 305 before finally reaching the coal mill body 2. Furthermore, the included angle between the two ends of the upper rectangular elbow 302 and the lower rectangular elbow 304 is also 90°. The specific structure is as follows: Figure 1 As shown.

[0039] As the core of this application, a flow-blocking component 4 is provided inside the air duct body 3 to prevent airflow from eroding the inner wall of the air duct body 3. Specifically, as shown in... Figure 1 As shown, the flow obstruction assembly 4 includes several vertical flow obstruction rings 5. The several vertical flow obstruction rings 5 ​​are parallel to each other and evenly distributed at equal intervals on the inner walls of the upper rectangular air duct 301 and the lower rectangular air duct 305, and the vertical flow obstruction rings 5 ​​are perpendicular to the inner walls of the upper rectangular air duct 301 and the lower rectangular air duct 305.

[0040] In addition, such as Figure 1-5 As shown, the flow-blocking assembly 4 also includes several inclined flow-blocking rings 6 and several curved flow-blocking plates 7 disposed inside the upper rectangular bend 302 and the lower rectangular bend 304, wherein:

[0041] Several inclined flow-blocking rings 6 are configured into two groups. Each group of inclined flow-blocking rings 6 is evenly arranged inside the upper rectangular elbow 302 and lower rectangular elbow 304, with the included angle α between any two adjacent inclined flow-blocking rings 6 as the axis, and 20° < α < 40°. The specific structure is as follows: Figure 2-5 As shown; in addition, the inner wall surfaces of the upper rectangular elbow 302 and the lower rectangular elbow 304 away from the vertex O of the bending angle are respectively the first wall surface 306 and the second wall surface 307. A number of curved flow-blocking plates 7 are evenly arranged on the first wall surface 306 and the second wall surface 307 of the upper rectangular elbow 302 and the lower rectangular elbow 304 with their extension direction coinciding with the flow direction of the hot air.

[0042] More specifically, in the flow-blocking component 4, such as Figure 6As shown, both the vertical flow-blocking ring 5 and the inclined flow-blocking ring 6 are formed by four rectangular flow-blocking unit plates 8, and the four flow-blocking unit plates 8 are welded and fixed to each other. In addition, the vertical flow-blocking ring 5, the inclined flow-blocking ring 6, and the curved flow-blocking plate 7 are also welded and fixed to the inner wall of the air duct body 3.

[0043] In the vertical flow-blocking ring 5 and the inclined flow-blocking ring 6, the length of the flow-blocking unit plate 8 matches the inner wall of the air duct body 3. The width of the flow-blocking unit plate 8 is L1, and 20mm < L1 < 50mm. The thickness of the flow-blocking unit plate 8 is L2, and 4mm < L2 < 10mm. The specific structure is as follows: Figure 6-7 As shown.

[0044] In the upper rectangular elbow 302 and the lower rectangular elbow 304, the width of the bending baffle 7 is L3, where 20mm < L3 < 50mm, and the thickness of the bending baffle 7 is L4, where 4mm < L4 < 10mm. The specific structure is as follows: Figure 8 As shown.

[0045] In the upper rectangular elbow 302 and the lower rectangular elbow 304, the distance between two adjacent bending baffles 7 is L5, and 200mm < L5 < 400mm; in the upper rectangular duct 301 and the lower rectangular duct 305, the distance between two adjacent vertical baffle rings 5 ​​is L6, and 200mm < L6 < 400mm. The specific structure is as follows: Figure 1 , Figure 8 As shown.

[0046] Based on the above core points, the limitation of the included angle α between two adjacent inclined flow-blocking rings 6, the limitation of the width L1 and thickness L2 of the flow-blocking unit plate 8, and the limitation of the width L3 and thickness L4 of the curved flow-blocking plate 7 are set in combination based on the properties of fluid mechanics in the prior art. That is, based on fluid mechanics, the coal mill air duct is designed according to the value range of the above quantities, and the resulting anti-airflow scouring effect is more significant, extending the service life of the air duct.

[0047] Specifically, based on the above structure, an airflow stagnation zone 9 is formed between two adjacent vertical obstruction rings 5 ​​in the upper rectangular air duct 301 and the lower rectangular air duct 305. The formation of the airflow stagnation zone 9 is due to the following: when the hot airflow reaches the vertical obstruction ring 5, the hot airflow cannot continue to flow along the inner wall of the air duct body 3 due to the obstruction of the vertical obstruction ring 5. Thus, the kinetic energy of the hot airflow is converted into potential energy, that is, the flow velocity decreases and the pressure increases. Therefore, an airflow stagnation zone 9 is formed in the area between two adjacent vertical obstruction rings 5, and an air film protective wind is formed in the airflow stagnation zone 9. The flow stagnation zone 9 has the high pressure characteristic brought about by the conversion of kinetic energy into potential energy. The pressure of the hot airflow outside the flow stagnation zone 9 is lower than that inside the flow stagnation zone 9. Therefore, the hot airflow outside the flow stagnation zone 9 cannot enter the flow stagnation zone 9, and the dust carried by the hot airflow will not enter the flow stagnation zone 9, so it will not cause erosion of the duct wall. On this basis, the air film protection wind refers to the air inside the flow stagnation zone 9. The air film protection wind isolates the inner wall of the duct body 3 from the hot airflow inside the duct body 3, which can prevent the hot airflow inside the duct body 3 from carrying dust and abrading the inner wall.

[0048] As another core aspect of this invention, this application also incorporates structural design at the upper rectangular bend 302 and lower rectangular bend 304, where the hot air flow field environment is more complex, to generate the airflow stagnation zone 9. Specifically, as follows... Figure 3 , Figure 5 As shown, in the upper rectangular bend 302 and the lower rectangular bend 304, each inclined flow-blocking ring 6 is configured with a flow-blocking unit plate 8 that is fixedly welded to the first wall surface 306 and the second wall surface 307 as a forming plate. Several forming plates and several curved flow-blocking plates 7 intersect each other to form several airflow stagnation zones 9 in an overall grid shape.

[0049] In addition, this application also adapts the specific structure of the partially inclined flow-blocking ring 6 to the formation method of the airflow stagnation zone 9 in fluid mechanics, such as... Figure 7 As shown, based on the flow direction of hot air inside the upper rectangular elbow 302 and the lower rectangular elbow 304, the angle between the angles formed by several inclined flow-blocking rings 6 and the first wall surface 306 and the second wall surface 307 in the windward direction is the windward angle β, where β ≤ 90°. To specifically accommodate the setting of the windward angle β, this application configures the main structure of the upper rectangular elbow 302 as a first air inlet 10 and a first air outlet 11 according to the sequential flow path of the hot air. Among the several inclined flow-blocking rings 6 located inside the upper rectangular elbow 302, some inclined flow-blocking rings 6 located inside the first air outlet 11 are at a fixed position to the first wall surface 306, forming a 90° angle with the first wall surface 306. That is, the forming plate of some inclined flow-blocking rings 6 located inside the first air outlet 11 is perpendicular to the first wall surface 306. The specific structure is as follows: Figure 2-5As shown; furthermore, the main body structure of the lower rectangular elbow 304 is configured as a second air inlet 12 and a second air outlet 13 according to the sequential flow path of hot air. Among the several inclined flow-blocking rings 6 located inside the lower rectangular elbow 304, some of the inclined flow-blocking rings 6 located inside the second air outlet 13 are at a position fixed to the second wall 307 and are also at 90° to the second wall 307. That is, the forming plate of some of the inclined flow-blocking rings 6 located inside the second air outlet 13 is perpendicular to the second wall 307.

[0050] Based on the above structure, this arrangement facilitates the formation of the airflow stagnation zone 9. From a fluid dynamics perspective, if the angle of attack β formed by the inclined flow-blocking ring 6 with the first wall surface 306 and the second wall surface 307 is greater than 90°, the hot airflow will generate a radial velocity component along the duct body 3 when it flows through the inclined flow-blocking ring 6. Even if this velocity is very low, it will still cause the hot airflow to flow along the surface of the inclined flow-blocking ring 6. This would not ensure the formation of the airflow stagnation zone 9, thereby destroying the protective air film near the inner wall surface of the duct body 3. Therefore, this application improves the structure of the inclined flow-blocking ring 6 to prevent the situation where the angle of attack β formed by the inclined flow-blocking ring 6 with the first wall surface 306 and the second wall surface 307 is greater than 90°, thus ensuring the smooth formation of the airflow stagnation zone 9 and ultimately achieving a good anti-scouring effect.

[0051] In this technical solution, the vertical flow-blocking ring 5, the inclined flow-blocking ring 6, and the curved flow-blocking plate 7 in the flow-blocking component 4 are all made of carbon steel, which provides a structural basis for the formation of the airflow stagnation zone 9 by utilizing its high hardness and high corrosion resistance.

[0052] In general, based on the actual working condition of hot air flowing sequentially through the upper rectangular air duct 301, the upper rectangular elbow 302, the vertical rectangular air duct 303, the lower rectangular elbow 304, and the lower rectangular air duct 305 and finally being transmitted to the coal mill body 2, the present invention sets several vertical flow-blocking rings 5 ​​inside the upper rectangular air duct 301 and the lower rectangular air duct 305, and based on the properties of fluid mechanics, forms an airflow stagnation zone 9 between any two adjacent vertical flow-blocking rings 5 ​​to prevent the hot air flow from scouring the inner walls of the upper rectangular air duct 301 and the lower rectangular air duct 305.

[0053] In addition, this application utilizes a combination of several inclined flow-blocking rings 6 and several curved flow-blocking plates 7 to form several airflow stagnation zones 9 in a grid-like pattern at the upper rectangular bend 302 and lower rectangular bend 304, where the hot airflow field environment is more complex. This further protects the inner wall of the duct body 3 using the airflow stagnation zones 9.

[0054] Based on this, in order to facilitate the formation of airflow stagnation zones 9 at the upper rectangular bend 302 and the lower rectangular bend 304, this application further limits the windward angle β formed by the inclined flow-blocking ring 6 with the first wall surface 306 and the second wall surface 307 to no more than 90°. In order to adapt to this limitation, this application also makes adaptive designs on the specific structure of some inclined flow-blocking rings 6 to prevent the windward angle β formed by the inclined flow-blocking ring 6 with the first wall surface 306 and the second wall surface 307 from being greater than 90°. The smooth formation of the airflow stagnation zone 9 ultimately achieves a good anti-scouring effect.

[0055] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coal mill air duct designed to prevent airflow erosion, disposed between a hot air header and the coal mill body, for transferring hot air supplied by the hot air header to the coal mill body, characterized in that, The coal mill air duct includes: The air duct body includes an upper rectangular air duct, an upper rectangular elbow, a vertical rectangular air duct, a lower rectangular elbow, and a lower rectangular air duct arranged in sequence. One end of the upper rectangular air duct is connected to the hot air main pipe, and one end of the lower rectangular air duct is connected to the coal mill body. The hot air provided by the hot air main pipe enters the air duct body from the upper rectangular air duct and passes through the upper rectangular elbow, the vertical rectangular air duct, the lower rectangular elbow, and the lower rectangular air duct in sequence before finally reaching the coal mill body. The two ends of the upper rectangular elbow are at a 90° angle, and the two ends of the lower rectangular elbow are also at a 90° angle. The flow obstruction assembly includes several vertical flow obstruction rings, which are parallel to each other and evenly distributed at equal intervals on the inner walls of the upper rectangular air duct and the lower rectangular air duct, and the vertical flow obstruction rings are perpendicular to the inner walls of the upper rectangular air duct and the lower rectangular air duct. The flow-blocking assembly further includes several inclined flow-blocking rings and several curved flow-blocking plates disposed inside the upper rectangular elbow and the lower rectangular elbow, wherein: Several inclined flow-blocking rings are configured into two groups, and each group of inclined flow-blocking rings is evenly arranged inside the upper and lower rectangular elbows with the apex of the bending angle of the upper and lower rectangular elbows as the axis, respectively, and the included angle between any two adjacent inclined flow-blocking rings is equal. The inner wall surfaces of the upper and lower rectangular elbows away from the apex of the bending angle are configured as the first wall surface and the second wall surface, respectively. Several curved flow-blocking plates are evenly arranged on the first and second wall surfaces of the upper and lower rectangular elbows with equal spacing, based on the extension direction coinciding with the flow direction of the hot air. The upper rectangular elbow's body structure is configured as a first air inlet and a first air outlet according to the sequential flow path of the hot air. Among the several inclined flow-blocking rings located inside the upper rectangular elbow, some of the inclined flow-blocking rings located inside the first air outlet are at a 90° angle to the first wall surface at a position fixed to the first wall surface. The lower rectangular elbow's body structure is configured as a second air inlet and a second air outlet according to the sequential flow path of the hot air. Among the several inclined flow-blocking rings located inside the lower rectangular elbow, some of the inclined flow-blocking rings located inside the second air outlet are at a 90° angle to the second wall surface at a position fixed to the second wall surface. Based on the flow direction of the hot air inside the upper and lower rectangular bends, the angle between the angles formed by the several inclined flow-blocking rings and the first and second walls in the windward direction is the windward angle β, where β ≤ 90°.

2. The coal mill air duct for preventing airflow erosion according to claim 1, characterized in that: In the flow-blocking assembly, the vertical flow-blocking ring and the inclined flow-blocking ring are both formed by four rectangular flow-blocking unit plates, and the four flow-blocking unit plates are welded and fixed to each other. The vertical flow-blocking ring, the inclined flow-blocking ring, and the curved flow-blocking plate are also welded and fixed to the inner wall of the air duct body.

3. A coal mill air duct for preventing airflow erosion according to claim 2, characterized in that: In the vertical flow-blocking ring and the inclined flow-blocking ring, the length of the flow-blocking unit plate matches the inner wall of the air duct body, the width of the flow-blocking unit plate is L1, and 20mm < L1 < 50mm, and the thickness of the flow-blocking unit plate is L2, and 4mm < L2 < 10mm.

4. A coal mill air duct for preventing airflow erosion according to claim 3, characterized in that: In the upper rectangular elbow and the lower rectangular elbow, the included angle between two adjacent inclined flow-blocking rings is α, and 20° < α < 40°.

5. A coal mill air duct for preventing airflow erosion according to claim 4, characterized in that: In the upper rectangular elbow and the lower rectangular elbow, the width of the bending baffle is L3, and 20mm < L3 < 50mm, and the thickness of the bending baffle is L4, and 4mm < L4 < 10mm.

6. A coal mill air duct for preventing airflow erosion according to claim 5, characterized in that: In the upper rectangular bend and the lower rectangular bend, the distance between two adjacent bending baffles is L5, and 200mm < L5 < 400mm.

7. A coal mill air duct for preventing airflow erosion according to claim 6, characterized in that: In the upper rectangular air duct and the lower rectangular air duct, the distance between two adjacent vertical flow-blocking rings is L6, and 200mm < L6 < 400mm.

8. A coal mill air duct for preventing airflow erosion according to claim 7, characterized in that: In the upper rectangular air duct and the lower rectangular air duct, an airflow stagnation zone is formed between two adjacent vertical flow obstruction rings.

9. A coal mill air duct for preventing airflow erosion according to claim 8, characterized in that: In the upper rectangular bend and the lower rectangular bend, each inclined flow-blocking ring is configured with a flow-blocking unit plate that is fixedly welded to the first wall and the second wall as a forming plate. Several forming plates and several curved flow-blocking plates intersect each other to form several airflow stagnation zones that are generally grid-like.

10. A coal mill air duct for preventing airflow erosion according to claim 9, characterized in that: In the flow-blocking assembly, the vertical flow-blocking ring, the inclined flow-blocking ring, and the curved flow-blocking plate are all made of carbon steel.

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