Medium-speed coal mill nozzle ring and design method thereof

Abstract

The invention 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 millstone through a bolt, the moving ring is composed of an inner cone, a middle cone, an outer cone and blades, and a first blade is arranged between the inner cone and the middle cone of the moving ring; a first blade is arranged between the middle cone and the outer cone, a second blade is arranged between the middle cone and the outer cone, the first blade and the second blade are in a space twisting mode, and the lower portion of the first blade and the lower portion of the second blade vertically extend into the air chamber and can evenly guide airflow in the annular air channel to all cavities of the movable ring. The edges of the movable ring, the static ring and the cover ring form a labyrinth type sealing structure, the nozzle ring reduces gap air leakage by increasing the air stroke, controlling the gap size and increasing the stroke direction, and meanwhile the probability that pebble coal enters a sealing gap can be reduced through the cover ring. The problems that due to the fact that an internal flow field of an existing medium-speed coal mill seriously deflects, local abrasion is serious, and unorganized air leakage is high are solved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mills, and in particular to a nozzle ring of a medium-speed coal mill and a design method thereof. Background Art

[0002] Conventional medium-speed mill cold primary air positive pressure direct blowing pulverizing system, the coal mill nozzle ring surrounds the grinding disc, and consists of two parts: the dynamic nozzle ring (fixed on the grinding disc) and the static nozzle ring (fixed on the barrel wall). This equipment has long had problems such as severe local wear of the dynamic and static air rings, roller brackets, barrel walls, and lining tiles, and uneven wind speed at the wind ring outlet, resulting in large primary air volume, high stone coal discharge, reduced coal mill output, and increased coal consumption per unit, which seriously affects the operation of the unit and increases a lot of inspection and maintenance workload.

[0003] like Figure 1 to Figure 3 As shown in the figure, there are local over-high and over-low wind speeds at the wind ring outlet. This is mainly because the primary hot air symmetrically enters the annular channel at the bottom of the wind ring and then enters the coal mill through the oblique nozzle of the wind ring. Two different air volume distribution situations occur in this process. The primary mixed air enters the two sides of the wind chamber under the wind ring of the coal mill through the primary air duct. When the primary air on the B side enters the coal mill through the wind ring nozzle channel, the flow direction of the primary air is less than 90° with the wind ring nozzle channel. Part of the primary wind kinetic energy and potential energy in this area are superimposed to form a wind speed at the nozzle in this area. The wind speed at this location is relatively high, and a high wind speed can easily cause local wear of the coal mill; when the primary air on the C side enters the coal mill through the wind ring nozzle channel, the flow direction of the primary air is greater than 90° with the wind ring nozzle channel. The kinetic energy of the primary wind in this area weakens the total energy entering the wind ring nozzle channel, resulting in a lower wind speed at this location. A lower wind speed can easily lead to a large amount of stone coal in this area.

[0004] When the amount of pebble coal is large, in order to reduce the amount of pebble coal, the primary air volume is increased. This operation mode leads to higher wind speeds in areas with high local wind speeds, which accelerates wear. At the same time, the primary air volume increases, the ignition of coal powder is delayed, the combustion of coal powder becomes worse, and the carbon content of fly ash increases. When the primary air volume increases, the resistance of the coal mill increases, which increases the power consumption rate of the coal mill and the power consumption rate of 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 medium-speed coal mill nozzle ring and a design method thereof.

[0006] A nozzle ring for a medium-speed coal mill comprises: a moving ring, a stationary ring, a cover ring and a bracket. The moving ring is a double-layer air duct structure. The moving ring comprises an inner cone, a middle cone and an outer cone which are arranged in sequence from the inside to the outside. A first blade is arranged between the inner cone and the middle cone of the moving ring, and a second blade is arranged between the middle cone and the outer cone. The first blade and the second blade are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring. The first blade and the second blade are arranged in a spatially twisted pattern. The inlet normal angles γ of the first blade and the second blade are both 90 degrees. The outlet normal angles β1 of the first blade and the outlet normal angles β2 of the second blade are both 40 degrees to 50 degrees, and the outlet normal angle β1 of the first blade is greater than the outlet normal angle β2 of the second blade. The lower parts of the first blade and the second blade extend vertically into the wind chamber. The stationary ring is fixed to the bracket by bolts. The bracket is arranged at the lower end of the stationary ring. The bracket is connected to the coal mill barrel wall by welding. The upper end of the stationary ring is arranged with a cover ring, and the cover ring is connected to the stationary ring by bolts.

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

[0008] Furthermore, the angle α1 between the inner cone in the dynamic ring and the horizontal direction 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 air duct is between the inner cone and the middle cone, the outer air duct is between the middle cone and the outer cone, the cross-sectional area of ​​the outer air duct of the dynamic ring is smaller than the cross-sectional area of ​​the inner air duct, and the inlet and outlet cross-sectional area ratio of the outer air duct is greater than the inlet and outlet cross-sectional area ratio of the inner air duct.

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

[0011] Furthermore, the dynamic ring, the stationary ring and the cover ring are all formed by integral casting of a high chromium alloy.

[0012] The present invention also includes a method for designing a nozzle ring of a medium-speed coal mill. The method is implemented based on a nozzle ring of a medium-speed coal mill described in any one of the above items. First, a dynamic ring connected to the grinding disc of the coal mill by bolts is designed. The dynamic ring is composed of an inner cone, a middle cone, an outer cone, a first blade and a second blade. The inner cone, the middle cone, the outer cone, the first blade and the second blade are all formed by integrated casting of a high-chromium alloy; a first blade is arranged between the inner cone and the middle cone, and a second blade is arranged between the middle cone and the outer cone. The first blade and the second blade are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring. The first blade and the second blade are formed by spatial distortion. The first blade and the second blade are arranged in a row, the inlet normal angle γ of the first blade and the second blade are both 90 degrees, the outlet normal angle β1 of the first blade and the outlet normal angle β2 of the second blade are both 40 degrees to 50 degrees, and the outlet normal angle β1 of the first blade is greater than the outlet normal angle β2 of the second blade; the lower parts of the first blade and the second blade extend vertically into the wind chamber; a static ring connected to the wall of the coal mill barrel is designed, the static ring is fixed to the bracket by bolts, the bracket is arranged at the lower end of the static ring, the bracket is fixed to the wall of the coal mill barrel by welding, a cover ring is arranged at the upper end of the static ring, and the cover ring is connected to the static ring by bolts; the edges of the dynamic ring, the static ring and the cover ring form a labyrinth sealing structure.

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

[0014] 1. The present invention provides a nozzle ring for a medium-speed coal mill and a design method thereof. The double-layer air duct structure of the dynamic ring can increase the wind speed. The different air inlet angles and wind speed designs of the first blade and the second blade can protect the cylinder wall of the coal mill, reduce the wear of the cylinder wall of the coal mill, and reduce the overflow of coal powder, reduce the discharge of stone coal in the wind chamber, eliminate the uneven distribution of the flow field of the entire wind ring nozzle, reduce the power consumption rate of the primary fan, reduce the maintenance cost, and have a significant improvement effect on the energy saving of the pulverizing system. The first blade and the second blade are both twisted angle blades. The twisted angle blade The blade structure has a flow balancing effect on the flow field of the wind ring nozzle while adjusting the pressure difference between the inlet and outlet of the wind ring. The first blade and the second blade extending into the wind chamber can divide the fluid in the wind chamber, balance the fluid in the annular air duct, and guide the primary wind into the air duct, thereby enhancing the flow balancing ability of the nozzle ring, achieving uniform outlet air volume and reducing local wear. The edges of the dynamic ring, static ring and cover ring of the nozzle ring form a labyrinth sealing structure. By increasing the wind distance, controlling the gap size and increasing the gap leakage along the distance, the existence of the cover ring can reduce the probability of stone coal entering the sealing gap.

[0015] 2. In the technical solution provided by the present invention, the rounded corner structure at the corners of the first blade and the second blade can effectively reduce ventilation resistance and energy loss, and the dynamic ring, static ring and cover ring made of high chromium alloy material are conducive to improving service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is the overall schematic diagram of the primary air flow of the existing coal mill;

[0018] Figure 2 It is a schematic diagram of the flow of primary air passing through the air ring nozzle on the air ring B side of the existing coal mill;

[0019] Figure 3 It is a schematic diagram of the flow of primary air passing through the air ring nozzle on the C side of the existing coal mill air ring;

[0020] Figure 4 This is a cross-sectional view of the dynamic ring, static ring, cover ring and bracket structure of the present invention;

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

[0022] Figure 6 This is a schematic diagram of the process of primary air passing through the air ring nozzle on the side of the dynamic ring B of the present invention;

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

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

[0025] Fig. 9 It is a cross-sectional view of the extended structure of the first blade and the second blade of the present invention.

[0026] Description of reference numerals:

[0027] 1-dynamic ring; 2-static ring; 3-cover ring; 4-bracket; 5-inner cone; 6-middle cone; 7-outer cone; 8-first blade; 9-second blade. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In addition, 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 to 9A medium-speed coal mill nozzle ring shown in the figure comprises: a dynamic ring 1, a static ring 2, a cover ring 3 and a bracket 4. The dynamic ring 1 is a double-layer air duct structure. The dynamic ring 1 comprises an inner cone 5, a middle cone 6 and an outer cone 7 which are arranged in sequence from the inside to the outside. A first blade 8 is arranged between the inner cone 5 and the middle cone 6 of the dynamic 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 spatially twisted manner. The inlet normal angle γ of the first blade 8 and the second blade 9 are both 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 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, which can change the jet direction and provide sealing protection wind while reducing the discharge of stone coal; the lower parts of the first blade 8 and the second blade 9 extend vertically into the wind chamber, which can The outlet flow rate of the nozzle ring is uniform. The static ring 2 is connected to the wall of the coal mill barrel. The static ring 2 is fixed on the bracket 4 by bolts. The bracket 4 is arranged at the lower end of the static ring 2. The bracket 4 is connected to the wall of the coal mill barrel by welding. A cover ring 3 is arranged at the upper end of the static ring 2. The bracket 4 is welded to the wall of the coal mill barrel. The cover ring 3 is connected to the static 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, and the extension length of the second blade 9 is b. The values ​​of a and b are determined according to the actual situation. The dynamic ring 1 is connected to the grinding disc of the coal mill, and the grinding disc is connected to the power output end of the engine in the coal mill. When the engine is working, the dynamic ring 1 rotates with the rotation of the grinding disc. The edges of the dynamic ring 1, the static ring 2 and the cover ring 3 of the nozzle ring form a labyrinth sealing structure. By increasing the wind distance and controlling the gap size and increasing the gap leakage along the way, the existence of the cover ring can reduce the probability of stone coal entering the sealing gap.

[0033] In the double-layer air duct structure of the nozzle ring and the dynamic ring 1 of the medium-speed coal mill, the different air inlet angles and wind speeds of the first blade 8 and the second blade 9 can protect the cylinder wall of the coal mill and reduce the wear of the cylinder wall of the coal mill. At the same time, it can reduce the spillage of coal powder, reduce the discharge of stone coal in the wind chamber, reduce the power consumption rate of the primary fan, and reduce the maintenance cost, which has a significant improvement effect on the energy saving of the pulverizing system; the first blade 8 and the second blade 9 are both twisted angle blades, and the lower parts of the first blade 8 and the second blade 9 extend vertically into the wind chamber, which can adjust the pressure difference between the inlet and outlet of the wind ring while adjusting the pressure difference between the inlet and outlet of the wind ring. The nozzle flow field has a flow balancing effect. The first blade 8 and the second blade 9 extend into the wind chamber, which can divide the fluid in the wind chamber, balance the fluid in the annular air duct, and guide the primary wind into the air duct, thereby enhancing the flow balancing ability of the nozzle ring, achieving uniform outlet air volume and reducing local wear. The static ring 1 and the dynamic ring 2 together constitute the wind ring. The design function of the first blade 8 and the second blade 9 extending into the wind chamber is divided into two parts. One is to form an annular segmentation group to divide the fluid in the wind chamber at the lower part of the wind ring, which plays a role in balancing the fluid in the wind chamber; the other is to guide the flow, such as Figure 6 and Figure 7 As shown, for the side of area B where the wind speed is higher at the outlet of the original air ring, when part of the primary air enters the side of the annular channel B at the lower part of the air ring, compared with the original air ring, after part of the primary air meets the extended parts of the first blade 8 and the second blade 9, the extended parts of the first blade 8 and the second blade 9 block and delay the primary air from entering the channel, thereby reducing the primary wind speed in this area and alleviating local wear in this area; when part of the primary air enters the side of the wind chamber C at the lower part of the air ring, the extended parts of the first blade 8 and the second blade 9 guide the air, and after the primary air meets the extended parts of the first blade 8 and the second blade 9, the speed direction of part of the primary air is reversed, which is superimposed with the wind volume potential energy in this area. Compared with the original air ring, a higher wind speed is formed to enter the coal mill through the nozzle air ring and the nozzle channel. The increase in wind speed 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 dynamic ring 1 is a double-layer air duct structure, a first blade 8 is arranged between the inner cone 5 and the middle cone 6 of the dynamic ring 1, 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 twisted form, 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; through integral 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 first blades 8 and the second blade 9 may be different.

[0035] like Figure 4 As shown, in this embodiment, the angle α1 between the inner cone 5 of the moving ring 1 and the horizontal direction is 70°~90°, the angle α2 between the middle cone 6 and the horizontal direction is 70°~90°, and the angle α3 between the outer cone 7 and the horizontal direction is 70°~90°; the inner cone 5 and the middle cone 6 of the moving ring 1 constitute an inner air duct, and the middle cone 6 and the outer cone 7 constitute an outer air duct. The lower part of the moving ring 1 is the air duct inlet, and the upper part of the moving ring 1 is the air duct outlet. The inlet area of ​​the inner air duct is 2~3 times the outlet area, and the inlet area of ​​the outer air duct is 3~5 times the outlet area, which is beneficial to increase the wind speed at the air duct outlet, and at the same time make the outer layer outlet wind speed greater than the inner layer, forming a protective wind, reducing the discharge of stone coal, reducing air leakage and reducing wear while 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, enhance swirl, and reduce the overflow of coal powder, thereby better protecting the cylinder wall of the coal mill and reducing the wear of the cylinder wall of the coal mill, while reducing the discharge of stone coal in the wind chamber, reducing the power consumption rate of the primary fan, and reducing maintenance costs.

[0037] like Figure 5 As shown, in this embodiment, the normal angle γ of the lower inlet of the first blade 8 and the second blade 9 is 90 degrees, which can better divide the fluid in the annular wind chamber and better uniformize the flow field at the wind ring nozzle, thereby better protecting the cylinder wall of the coal mill, reducing local wear, and reducing the discharge of stone coal, eliminating the uneven phenomenon of the entire wind ring nozzle, reducing the power consumption rate of the primary 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 the cross-sectional area of ​​the inner air duct; and the inlet and outlet cross-sectional area ratio of the outer air duct is greater than the inlet and outlet cross-sectional area ratio of the inner air duct, which increases the protective wind without affecting the normal discharge of coal powder.

[0039] like Figure 5 As shown, in this embodiment, the corners of the first blade 8 and the second blade 9 are rounded structures; the rounded structures at the 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 dynamic ring 1, the stationary ring 2 and the cover ring 3 are all made of high-chromium alloy casting; the high-chromium alloy material has high strength, good wear resistance and oxidation resistance, which is beneficial to improving the service life of the dynamic 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 wall of the coal mill barrel 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. The edges of the dynamic ring 1, the stationary ring 2 and the cover ring 3 of the nozzle ring form a labyrinth sealing structure. By increasing the wind distance and controlling the gap size and increasing the gap leakage along the way, the existence of the cover ring can reduce the probability of stone coal entering the sealing gap and reduce the seal wear.

[0042] like Figures 4 to 9 As shown, the present invention also includes a design method for a nozzle ring of a medium-speed coal mill, which is implemented based on a nozzle ring of a medium-speed coal mill described in any one of the above items. First, a dynamic ring 1 connected to a grinding disc of a coal mill by bolts is designed, and the dynamic ring 1 is composed 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, the middle cone 6, the outer cone 7, the first blade 8 and the second blade 9 are all formed by integrated casting of a high-chromium alloy; 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. The first blade 8 and the second blade 9 are arranged in 36 to 48 groups along the circumferential direction of the nozzle ring, and the first blade 8 and the second blade 9 are arranged in a spatially twisted manner. The inlet normal angles γ of the two blades 9 are both 90 degrees, the outlet normal angles β1 of the first blade 8 and the outlet normal angles 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 wind chamber; a static ring 2 connected to the wall of the coal mill barrel is designed, the static ring 2 is fixed to the bracket 4 by bolts, the bracket 4 is arranged at the lower end of the static ring 2, the bracket 4 is connected to the wall of the coal mill barrel by welding, a cover ring 3 is arranged at the upper end of the static ring 2, and the cover ring 3 is connected to the static ring 2 by bolts; the edges of the dynamic ring 1, the static ring 2 and the cover ring 3 form a labyrinth sealing structure, which reduces the gap leakage by increasing the wind distance, controlling the gap size and increasing the gap along the distance.

[0043] like Figure 6 and Figure 7 As shown, in this embodiment, the gas flow is as follows Figure 6 and Figure 7As shown, for the side of area B where the wind speed is higher at the outlet of the original air ring, when part of the primary air enters the side of the annular channel B at the lower part of the air ring, compared with the original air ring, after part of the primary air meets the extended parts of the first blade 8 and the second blade 9, the extended parts of the first blade 8 and the second blade 9 block and delay the primary air from entering the channel, thereby reducing the primary wind speed in this area and alleviating local wear in this area; when part of the primary air enters the side of the wind chamber C at the lower part of the air ring, the extended parts of the first blade 8 and the second blade 9 guide the air, and after the primary air meets the extended parts of the first blade 8 and the second blade 9, the speed direction of part of the primary air is reversed, which is superimposed with the wind volume potential energy in this area. Compared with the original air ring, a higher wind speed is formed to enter the coal mill through the nozzle air ring and the nozzle channel. The increase in wind speed in this area can reduce the amount of stone coal in this area.

[0044] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A nozzle ring for a medium-speed coal mill, comprising: A moving ring (1), a stationary ring (2), a cover ring (3) and a bracket (4), characterized in that the moving ring (1) is a double-layer air duct structure, the moving ring (1) comprises an inner cone (5), a middle cone (6) and an outer cone (7) arranged in sequence 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), 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 spatially twisted pattern, and the first blade (8) and the second blade (9) are arranged in a spatially twisted pattern. ) are both 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) vertically extend into the wind chamber; 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 the bracket (4) is connected to the wall of the coal mill barrel 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. A nozzle ring for a medium speed coal mill according to claim 1, characterized in that: A labyrinth-type sealing structure is formed at the edges of the dynamic ring (1), the static ring (2) and the cover ring (3).

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

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

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

6. The nozzle ring of a medium speed coal mill according to claim 1, characterized in that: The dynamic ring (1), the static ring (2) and the cover ring (3) are all formed by integral casting of a high chromium alloy.

7. A method for designing a nozzle ring of a medium-speed coal mill, the method being implemented based on the nozzle ring of a medium-speed coal mill as claimed in any one of claims 1 to 6, characterized in that: First, a dynamic ring (1) connected to a grinding disc of a coal mill by bolts is designed. The dynamic ring (1) is composed 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), the middle cone (6), the outer cone (7), the first blade (8) and the second blade (9) are all formed by integrated casting of a high chromium alloy. 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). 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 spatially twisted manner. The inlet normals of the first blade (8) and the second blade (9) are 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) vertically extend into the wind chamber; a stationary ring (2) connected to the wall of the coal mill barrel is designed, 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 the bracket (4) is fixed to the wall of the coal mill barrel 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; the edges of the dynamic ring (1), the stationary ring (2) and the cover ring (3) form a labyrinth sealing structure.

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