A medium speed coal mill nozzle ring and a design method thereof

Abstract

The application provides a medium-speed coal mill nozzle ring and a design method thereof, and relates to the technical field of coal mills.The nozzle ring comprises a moving ring, a static ring, a cover ring and a support.The moving ring is connected with a grinding disc through bolts.The moving ring is composed of an inner cone, a middle cone, an outer cone and a blade.The first blade is arranged between the inner cone and the middle cone of the moving ring, and the second blade is arranged between the middle cone and the outer cone.The first blade and the second blade adopt a spatial twist type.The lower part of the first blade and the second blade vertically extends into the air chamber, which can uniformly guide the airflow in the annular air duct to each cavity of the moving ring.The cover ring is connected with the static ring through bolts.The edge of the moving ring, the static ring and the cover ring forms a labyrinth seal structure.The nozzle ring can reduce the probability of stone coal entering the sealing gap by increasing the air path, controlling the gap size and increasing the gap air leakage along the path while the cover ring exists, and solves the problems of serious local wear and unorganized air leakage caused by the serious deflection of the internal flow field of the existing medium-speed coal mill.

Description

Technical Field

[0001] This invention relates to the field of coal mill technology, specifically to a nozzle ring for a medium-speed coal mill and its design method. Background Technology

[0002] In a conventional medium-speed cold primary air positive pressure direct-fired pulverizing system, the pulverizer nozzle rings surround the grinding disc and consist of two parts: a moving nozzle ring (fixed to the grinding disc) and a stationary nozzle ring (fixed to the barrel wall). This equipment has long suffered from severe wear and tear on the moving and stationary air rings, grinding roller supports, barrel wall, and liners, as well as uneven air velocity at the air ring outlet. This results in high primary air volume, high stone coal discharge, decreased pulverizer output, and increased coal consumption per unit area, severely impacting unit operation and significantly increasing maintenance workload.

[0003] like Figures 1-3 As shown, the phenomenon of locally high and locally low wind speeds at the air ring outlet is mainly due to the fact that after the primary hot air symmetrically enters the annular channel at the bottom of the air ring, it enters the coal mill through the inclined nozzle of the air ring. During this process, two different air volume distribution scenarios occur. The primary air mixed with the air enters both sides of the lower air chamber of the coal mill air ring through the primary air duct. When the primary air on side B enters the coal mill through the air ring nozzle channel, the angle between the flow direction of the primary air and the air ring nozzle channel is less than 90°. In this area, the kinetic energy and potential energy of the primary air are superimposed, forming the wind speed at the nozzle in this area. The wind speed at this location is relatively high, which can easily cause local wear of the coal mill. When the primary air on side C enters the coal mill through the air ring nozzle channel, the angle between the flow direction of the primary air and the air ring nozzle channel is greater than 90°. The kinetic energy of the primary air in this area weakens the total energy entering the air ring nozzle channel at this location, resulting in a lower wind speed. The lower wind speed can easily lead to a large amount of gravel coal in this area.

[0004] When the amount of coke and gravel is large, the primary air volume is increased to reduce it. This operation mode results in even higher wind speeds in areas with already high wind speeds, accelerating wear. Simultaneously, the increased primary air volume delays pulverized coal ignition, worsens combustion, and increases the carbon content of fly ash. The increased primary air volume also increases the resistance of the coal mill, thus increasing the power consumption of both the mill and the primary air. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a nozzle ring for a medium-speed coal mill and its design method.

[0006] A nozzle ring for a medium-speed coal mill includes a moving ring, a stationary ring, a cover ring, and a support. The moving ring has a double-layer air duct structure and includes an inner cone, a middle cone, and an outer cone arranged sequentially from the inside to the outside. A first blade is disposed between the inner and middle cones, and a second blade is disposed between the middle and outer cones. 36 to 48 sets of both the first and second blades are arranged along the circumferential direction of the nozzle ring. The first and second blades are arranged in a spatially twisted pattern. The inlet normal angle γ of both the first and second blades is 90 degrees, and the outlet normal angles β1 and β2 of both the first and second blades are 40 to 50 degrees, with the first blade's outlet normal angle β1 being greater than the second blade's outlet normal angle β2. The lower parts of the first and second blades extend vertically into the air chamber. The stationary ring is fixed to the support by bolts, and the support is located at the lower end of the stationary ring and connected to the coal mill cylinder wall by welding. A cover ring is disposed at the upper end of the stationary ring and is connected to the stationary ring by bolts.

[0007] Furthermore, a labyrinth-type sealing structure is formed at the edges of the moving ring, the stationary ring, and the cover ring.

[0008] Furthermore, the angle α1 between the inner cone and the horizontal direction in the moving ring is 70° to 90°, the angle α2 between the middle cone and the horizontal direction is 70° to 90°, and the angle α3 between the outer cone and the horizontal direction is 70° to 90°.

[0009] Furthermore, the inner cone and the middle cone form an inner air duct, and the middle cone and the outer cone form an outer air duct. The cross-sectional area of ​​the outer air duct is smaller than that of the inner air duct, and the ratio of the inlet and outlet cross-sectional areas of the outer air duct is greater than that of the inner air duct.

[0010] Furthermore, the corners of the first and second blades are rounded.

[0011] Furthermore, the moving ring, stationary ring, and cover ring are all integrally cast from high-chromium alloy.

[0012] This invention also includes a design method for a nozzle ring of a medium-speed coal mill. This method is based on the nozzle ring of a medium-speed coal mill described in any of the preceding claims. First, a moving ring is designed, which is connected to the coal mill disc by bolts. The moving ring consists of an inner cone, a middle cone, an outer cone, a first blade, and a second blade. The inner cone, middle cone, outer cone, first blade, and second blade are all integrally cast from high-chromium alloy. A first blade is positioned between the inner and middle cones, and a second blade is positioned between the middle and outer cones. 36 to 48 sets of both the first and second blades are arranged along the circumferential direction of the nozzle ring. The first and second blades are arranged in a spatially twisted pattern. The first and second blades are arranged in a row, with the inlet normal angle γ of the first and second blades both being 90 degrees, and the outlet normal angles β1 and β2 of the first and second blades both being 40 to 50 degrees, with the outlet normal angle β1 of the first blade being greater than the outlet normal angle β2 of the second blade. The lower parts of the first and second blades extend vertically into the air chamber. A stationary ring is designed to be connected to the wall of the coal mill. The stationary ring is fixed to a support by bolts. The support is arranged at the lower end of the stationary ring and is fixed to the wall of the coal mill by welding. A cover ring is arranged at the upper end of the stationary ring, and the cover ring is connected to the stationary ring by bolts. The edges of the moving ring, the stationary ring, and the cover ring form a labyrinth-type sealing structure.

[0013] The technical solution of this invention has the following advantages:

[0014] 1. This invention provides a nozzle ring for a medium-speed coal mill and its design method. The double-layer air duct structure of the moving ring can improve the air velocity. The different air inlet angles and air velocities of the first and second blades can protect the mill cylinder wall, reduce wear, reduce coal powder overflow, reduce the amount of stone coal discharged from the air chamber, eliminate the uneven distribution of the flow field at the nozzle of the entire air ring, reduce the power consumption of the primary air fan, and reduce maintenance costs. It has a significant improvement effect on energy saving of the pulverizing system. Both the first and second blades are twisted angled blades. The blade structure regulates the pressure difference between the inlet and outlet of the air ring while also equalizing the flow field at the nozzle of the air ring. The first and second blades extend into the air chamber to divide the fluid in the air chamber, equalize the flow of the fluid in the annular air duct, and guide the primary air into the air duct, thereby enhancing the flow equalization capability of the nozzle ring, achieving uniform outlet air volume, and reducing local wear. The edges of the moving ring, stationary ring, and cover ring of the nozzle ring form a labyrinth-type sealing structure. By increasing the air path, controlling the gap size, and increasing the friction distance to reduce gap leakage, the presence of the cover ring can reduce the probability of stones and coal entering the sealing gap.

[0015] 2. In the technical solution provided by the present invention, the rounded corner structure at the bend of the first blade and the second blade can effectively reduce ventilation resistance and energy loss, and the moving ring, stationary ring and cover ring made of high chromium alloy material are conducive to improving service life. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the primary air flow process of an existing coal mill.

[0018] Figure 2 A schematic diagram of the primary air flow through the air ring nozzle on the B side of the existing coal mill air ring.

[0019] Figure 3 A schematic diagram of the primary air flow through the air ring nozzle on the C side of an existing coal mill air ring.

[0020] Figure 4 This is a cross-sectional view of the moving ring, stationary ring, cover ring, and support structure of the present invention;

[0021] Figure 5 This is a schematic diagram of the structure of the first and second blades of the present invention;

[0022] Figure 6 This is a schematic diagram of the primary air flow through the air ring nozzle on the B side of the dynamic ring according to the present invention.

[0023] Figure 7 This is a schematic diagram of the primary air flow through the air ring nozzle on the C side of the dynamic ring according to the present invention;

[0024] Figure 8 This is a schematic diagram of the overall structure of the present invention;

[0025] Figure 9 This is a cross-sectional view of the extended structure of the first and second blades of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1-Moving ring; 2-Stationary ring; 3-Cover ring; 4-Support; 5-Inner cone; 6-Middle cone; 7-Outer cone; 8-First blade; 9-Second blade. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0029] 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. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figures 4-9The nozzle ring of a medium-speed coal mill shown includes: a moving ring 1, a stationary ring 2, a cover ring 3, and a support 4. The moving ring 1 has a double-layer air duct structure and includes an inner cone 5, a middle cone 6, and an outer cone 7 arranged sequentially from the inside to the outside. A first blade 8 is arranged between the inner cone 5 and the middle cone 6, and a second blade 9 is arranged between the middle cone 6 and the outer cone 7. 36 to 48 sets of both the first blade 8 and the second blade 9 are arranged along the circumferential direction of the nozzle ring. The first blade 8 and the second blade 9 are arranged in a spatially twisted pattern. The inlet normal angle γ of both the first blade 8 and the second blade 9 is 90 degrees, and the outlet normal angle β1 of the first blade 8 and the outlet normal angle β2 of the second blade 9 are both 40 to 50 degrees. The outlet normal angle β1 of the first blade 8 is greater than the outlet normal angle β2 of the second blade 9, which can change the jet direction and provide sealing protection air while reducing the amount of stone coal discharged. The lower parts of the first blade 8 and the second blade 9 extend vertically into the air chamber, enabling... The uniform nozzle ring outlet velocity, the stationary ring 2 is connected to the coal mill cylinder wall, the stationary ring 2 is fixed to the bracket 4 by bolts, the bracket 4 is arranged at the lower end of the stationary ring 2, the bracket 4 is connected to the coal mill cylinder wall by welding, the upper end of the stationary ring 2 is provided with a cover ring 3, the bracket 4 is welded to the coal mill cylinder wall, the cover ring 3 is connected to the stationary ring 2 by bolts, the specific number of the first blade 8 and the second blade 9 is adjusted according to the actual situation, the extension length of the first blade 8 is a, the extension length of the second blade 9 is b, the values ​​of a and b are determined according to the actual situation, the moving ring 1 is connected to the grinding disc of the coal mill, the grinding disc is connected to the power output end of the engine in the coal mill, when the engine is working, the moving ring 1 rotates with the rotation of the grinding disc, the edges of the moving ring 1, stationary ring 2 and cover ring 3 of the nozzle ring form a labyrinth-type sealing structure, by increasing the air path and controlling the gap size and increasing the path to reduce gap leakage, while the presence of the cover ring can reduce the probability of stones and coal entering the sealing gap.

[0033] In the aforementioned medium-speed coal mill nozzle ring and the double-layer air duct structure of the moving ring 1, the different air inlet angles and air velocities of the first blade 8 and the second blade 9 protect the mill cylinder wall, reduce wear, reduce coal powder spillage, reduce the amount of stone coal discharged from the air chamber, lower the primary air fan power consumption, and reduce maintenance costs, thus significantly improving energy saving in the pulverizing system. Both the first blade 8 and the second blade 9 are twisted angled blades, with their lower parts extending vertically into the air chamber, which can adjust the pressure difference between the inlet and outlet of the air ring while simultaneously regulating the air ring's performance. The nozzle flow field has a flow equalization effect. The first blade 8 and the second blade 9 extend into the air chamber, which can divide the fluid in the air chamber, equalize the fluid in the annular air duct, and guide the primary air into the air duct, enhancing the flow equalization capability of the nozzle ring, achieving uniform outlet air volume and reducing local wear. The stationary ring 1 and the moving ring 2 together form the air ring. The design function of the first blade 8 and the second blade 9 extending into the air chamber is twofold: first, to form an annular dividing group, dividing the fluid in the lower part of the air chamber of the air ring, thus achieving the function of equalizing the fluid in the air chamber; second, to guide the flow, such as... Figure 6 and Figure 7 As shown, for the area B with a higher air velocity at the outlet of the original air ring, when some primary air enters the annular channel B at the bottom of the air ring, compared to the original air ring, after some primary air encounters the extended portions of the first blade 8 and the second blade 9, the extended portions of the first blade 8 and the second blade 9 have the effect of blocking and delaying the entry of primary air into the channel, reducing the primary air velocity in this area and alleviating local wear in this area; when some primary air enters the air chamber C at the bottom of the air ring, the extended portions of the first blade 8 and the second blade 9 have a guiding effect. After the primary air encounters the extended portions of the first blade 8 and the second blade 9, the velocity direction of some primary air reverses, and it superimposes with the air volume potential energy in this area, forming a higher air velocity than the original air ring, which enters the coal mill through the nozzle air ring and nozzle channel. The increase in air velocity in this area can reduce the amount of stone coal in this area.

[0034] like Figure 4 and Figure 8 As shown, in this embodiment, the moving ring 1 has a double-layer air duct structure. A first blade 8 is provided between the inner cone 5 and the middle cone 6 of the moving ring 1, and a second blade 9 is provided between the middle cone 6 and the outer cone 7. The first blade 8 and the second blade 9 are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring. The first blade 8 and the second blade 9 are arranged in a spatial twisted pattern. The inner cone 5, the middle cone 6, the outer cone 7, the first blade 8 and the second blade 9 are all integrally cast. The middle cone 6 is mainly used to separate the inner and outer air ducts and to install the first blade 8 and the second blade 9. By integrally casting, the stability of the connection between the inner cone 5, the middle cone 6, the outer cone 7, the first blade 8 and the second blade 9 can be effectively increased, and the connection strength can be increased. The number of the first blade 8 and the second blade 9 may vary.

[0035] like Figure 4 As shown, in this embodiment, the angle α1 between the inner cone 5 and the horizontal direction of the moving ring 1 is 70° to 90°, the angle α2 between the middle cone 6 and the horizontal direction is 70° to 90°, and the angle α3 between the outer cone 7 and the horizontal direction is 70° to 90°. The inner cone 5 and the middle cone 6 of the moving ring 1 constitute the inner air duct, and the middle cone 6 and the outer cone 7 constitute the outer air duct. The air duct inlet is below the moving ring 1, and the air duct outlet is above the moving ring 1. The inlet area of ​​the inner air duct is 2 to 3 times the outlet area, and the inlet area of ​​the outer air duct is 3 to 5 times the outlet area. This is beneficial to increase the air velocity at the air duct outlet, and at the same time, make the outer outlet air velocity greater than the inner one, forming a protective air, reducing the amount of stone and coal discharged, reducing air leakage, reducing wear, and reducing the power consumption rate of the primary fan.

[0036] like Figure 5 As shown, in this embodiment, the outlet normal angle β1 of the first blade 8 and the outlet normal angle β2 of the second blade 9 are both 40 degrees to 50 degrees, and the outlet normal angle β1 of the first blade 8 is greater than the outlet normal angle β2 of the second blade 9. This helps to form different jet directions inside and outside, enhances the swirling flow, reduces the overflow of coal powder, thereby better protecting the mill wall, reducing the wear of the mill wall, and at the same time reducing the amount of stone coal discharged from the air chamber, reducing the power consumption rate of the primary air fan, and reducing maintenance costs.

[0037] like Figure 5 As shown, in this embodiment, the lower inlet normal angle γ of the first blade 8 and the second blade 9 is 90 degrees, which can better divide the fluid in the annular air chamber and play a better role in uniformizing the flow field at the air ring nozzle, thereby better protecting the cylinder wall of the coal mill, reducing local wear, reducing the amount of stone coal discharged, eliminating the unevenness of the entire air ring nozzle, reducing the power consumption rate of the primary air fan, and reducing maintenance costs.

[0038] like Figure 8 As shown, in this embodiment, the cross-sectional area of ​​the outer air duct of the dynamic ring 1 is smaller than that of the inner air duct; and the ratio of the inlet and outlet cross-sectional areas of the outer air duct is greater than that of the inlet and outlet cross-sectional areas of the inner air duct, so as to increase the protective air without affecting the normal discharge of pulverized coal.

[0039] like Figure 5 As shown in this embodiment, the corners of the first blade 8 and the second blade 9 are rounded; the rounded corners of the first blade 8 and the second blade 9 can effectively reduce ventilation resistance, reduce energy loss, and reduce wear.

[0040] like Figure 4 As shown, in this embodiment, the moving ring 1, the stationary ring 2, and the cover ring 3 are all made of high-chromium alloy casting. High-chromium alloy material has high strength, good wear resistance, and oxidation resistance, which is beneficial to improving the service life of the moving ring 1, the stationary ring 2, and the cover ring 3.

[0041] like Figure 4 As shown, in this embodiment, the stationary ring 2 is fixed to the bracket 4 by bolts. The bracket 4 is arranged at the lower end of the stationary ring 2 and is connected to the coal mill cylinder wall by welding. The upper end of the stationary ring 2 is provided with a cover ring 3, which is connected to the stationary ring 2 by bolts. The edges of the moving ring 1, the stationary ring 2 and the cover ring 3 of the nozzle ring form a labyrinth-type sealing structure. By increasing the airflow and controlling the gap size and increasing the airflow along the path to reduce gap leakage, the presence of the cover ring can reduce the probability of stones and coal entering the sealing gap and reduce seal wear.

[0042] like Figures 4-9 As shown, the present invention also includes a design method for a nozzle ring of a medium-speed coal mill. This method is based on a nozzle ring for a medium-speed coal mill as described in any of the above claims. First, a moving ring 1 is designed and connected to the grinding disc of the coal mill by bolts. The moving ring 1 consists of an inner cone 5, a middle cone 6, an outer cone 7, a first blade 8, and a second blade 9. The inner cone 5, middle cone 6, outer cone 7, first blade 8, and second blade 9 are all integrally cast from high-chromium alloy. A first blade 8 is provided between the inner cone 5 and the middle cone 6, and a second blade 9 is provided between the middle cone 6 and the outer cone 7. 36 to 48 sets of first blades 8 and second blades 9 are arranged along the circumferential direction of the nozzle ring. The first blades 8 and second blades 9 are arranged in a spatially twisted pattern. The inlet normal angle γ of both blades 9 is 90 degrees. The outlet normal angles β1 and β2 of the first blade 8 and the second blade 9 are both 40 to 50 degrees, and the outlet normal angle β1 of the first blade 8 is greater than the outlet normal angle β2 of the second blade 9. The lower parts of the first blade 8 and the second blade 9 extend vertically into the air chamber. A stationary ring 2 connected to the coal mill cylinder wall is designed. The stationary ring 2 is fixed to the support 4 by bolts. The support 4 is arranged at the lower end of the stationary ring 2 and is connected to the coal mill cylinder wall by welding. A cover ring 3 is arranged at the upper end of the stationary ring 2. The cover ring 3 is connected to the stationary ring 2 by bolts. The edges of the moving ring 1, the stationary ring 2 and the cover ring 3 form a labyrinth-type sealing structure. By increasing the airflow and controlling the gap size and increasing the flow path, the gap leakage is reduced.

[0043] like Figure 6 and Figure 7 As shown in the figure, in this embodiment, the gas flow is as follows: Figure 6 and Figure 7As shown, for the area B with a higher air velocity at the outlet of the original air ring, when some primary air enters the annular channel B at the bottom of the air ring, compared to the original air ring, after some primary air encounters the extended portions of the first blade 8 and the second blade 9, the extended portions of the first blade 8 and the second blade 9 have the effect of blocking and delaying the entry of primary air into the channel, reducing the primary air velocity in this area and alleviating local wear in this area; when some primary air enters the air chamber C at the bottom of the air ring, the extended portions of the first blade 8 and the second blade 9 have a guiding effect. After the primary air encounters the extended portions of the first blade 8 and the second blade 9, the velocity direction of some primary air reverses, and it superimposes with the air volume potential energy in this area, forming a higher air velocity than the original air ring, which enters the coal mill through the nozzle air ring and nozzle channel. The increase in air velocity in this area can reduce the amount of stone coal in this area.

[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A nozzle ring for a medium-speed coal mill, comprising: The moving ring (1), stationary ring (2), cover ring (3), and bracket (4) are characterized in that the moving ring (1) is a double-layer air duct structure, the moving ring (1) includes an inner cone (5), a middle cone (6), and an outer cone (7) arranged sequentially from the inside to the outside, a first blade (8) is arranged between the inner cone (5) and the middle cone (6) of the moving ring (1), and a second blade (9) is arranged between the middle cone (6) and the outer cone (7), the first blade (8) and the second blade (9) are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring, the first blade (8) and the second blade (9) are arranged in a spatial twisting pattern, the first blade (8) and the second blade (9) are arranged in a spatial twisting pattern. The inlet normal angle γ of the first blade (8) and the outlet normal angle β1 of the first blade (8) and the outlet normal angle β2 of the second blade (9) are both 40 degrees to 50 degrees, and the outlet normal angle β1 of the first blade (8) is greater than the outlet normal angle β2 of the second blade (9); the lower parts of the first blade (8) and the second blade (9) extend vertically into the air chamber; the stationary ring (2) is fixed to the support (4) by bolts, the support (4) is arranged at the lower end of the stationary ring (2), and the support (4) is connected to the coal mill cylinder wall by welding; a cover ring (3) is arranged at the upper end of the stationary ring (2), and the cover ring (3) is connected to the stationary ring (2) by bolts.

2. The nozzle ring for a medium-speed coal mill according to claim 1, characterized in that, The edges of the moving ring (1), the stationary ring (2), and the cover ring (3) form a labyrinth-type sealing structure.

3. The nozzle ring for a medium-speed coal mill according to claim 1, characterized in that, The inner cone (5) of the moving ring (1) has an angle α1 of 70° to 90° with the horizontal direction, the middle cone (6) has an angle α2 of 70° to 90° with the horizontal direction, and the outer cone (7) has an angle α3 of 70° to 90° with the horizontal direction.

4. A nozzle ring for a medium-speed coal mill according to claim 1, characterized in that, The inner cone (5) and the middle cone (6) form an inner air duct, and the middle cone (6) and the outer cone (7) form an outer air duct. The cross-sectional area of ​​the outer air duct of the moving ring (1) is smaller than that of the inner air duct, and the ratio of the inlet and outlet cross-sectional areas of the outer air duct is greater than that of the inlet and outlet cross-sectional areas of the inner air duct.

5. A nozzle ring for a medium-speed coal mill according to claim 1, characterized in that, The corners of the first blade (8) and the second blade (9) are rounded.

6. A nozzle ring for a medium-speed coal mill according to claim 1, characterized in that, The moving ring (1), stationary ring (2) and cover ring (3) are all integrally cast from high chromium alloy.

7. A design method for a nozzle ring of a medium-speed coal mill, the method being implemented based on a nozzle ring for a medium-speed coal mill as described in any one of claims 1 to 6, characterized in that... First, a moving ring (1) connected to the grinding disc of the coal mill via bolts is designed. The moving ring (1) consists of an inner cone (5), a middle cone (6), an outer cone (7), a first blade (8), and a second blade (9). The inner cone (5), middle cone (6), outer cone (7), first blade (8), and second blade (9) are all integrally cast from high-chromium alloy. The first blade (8) is located between the inner cone (5) and the middle cone (6), and the second blade (9) is located between the middle cone (6) and the outer cone (7). The first blade (8) and the second blade (9) are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring. The first blade (8) and the second blade (9) are arranged in a spatial twisted pattern. The inlet normal of the first blade (8) and the second blade (9) The angle γ is 90 degrees. The outlet normal angle β1 of the first blade (8) and the outlet normal angle β2 of the second blade (9) are both 40 degrees to 50 degrees, and the outlet normal angle β1 of the first blade (8) is greater than the outlet normal angle β2 of the second blade (9). The lower parts of the first blade (8) and the second blade (9) extend vertically into the air chamber. A stationary ring (2) connected to the wall of the coal mill is designed. The stationary ring (2) is fixed to the support (4) by bolts. The support (4) is arranged at the lower end of the stationary ring (2). The support (4) is fixed to the wall of the coal mill by welding. A cover ring (3) is arranged at the upper end of the stationary ring (2). The cover ring (3) is connected to the stationary ring (2) by bolts. The edges of the moving ring (1), the stationary ring (2) and the cover ring (3) form a labyrinth-type sealing structure.

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