Vertical roller mill

Abstract

Provided is a vertical roller mill in which the flow of gas rising within a mill housing is made uniform in the circumferential direction while suppressing pressure loss. The vertical roller mill has a rotating table, a pulverizing roller disposed on the upper surface of the rotating table, a separator having a classification rotor disposed above the rotating table, which classifies pulverized material that has been pneumatically conveyed after being pulverized by the rotating table and the pulverizing roller, a mill housing that houses the rotating table, the pulverizing roller, and the separator, which has an exhaust port disposed above the separator, an annular flow path in the shape of a torus that surrounds the outer periphery of the rotating table, at least one gas introduction duct that blows hot gas having a velocity component in the tangential direction of the annular flow path in a flow path cross section of the annular flow path toward the flow path cross section of the annular flow path, and a hot gas nozzle in the shape of a torus that surrounds the outer periphery of the rotating table, which blows up the hot gas of the annular flow path from the outer periphery of the rotating table.

Description

Technical Field

[0001] This disclosure relates to a vertical roller mill with a separator. Background Technology

[0002] Previously, vertical roller mills were used for crushing solid fuels such as coal and cement raw materials such as limestone or clay. Hereinafter, the material being crushed in a vertical roller mill will be referred to as the raw material, and the crushed raw material will be referred to as the pulverized material. Among vertical roller mills, there are those equipped with separators that classify the pulverized material to adjust the particle size of the product.

[0003] A vertical roller mill has a rotating worktable and crushing rollers that are elastically pressed against the rotating worktable. Raw materials are bitten between the rotating worktable and the crushing rollers and crushed. The crushed material moves towards the edge of the rotating worktable and rises within the mill casing accompanied by hot air blown from around the worktable. It is then separated into fine and coarse powder by a separator. The fine powder, along with the gas, is discharged from the outlet at the top of the mill casing, while the coarse powder is crushed again along with the raw material. To improve the separation efficiency, it is preferable that the airflow accompanying the crushed material flows into the separator without deviation.

[0004] Therefore, in the vertical roller mill of Patent Document 1, it has: an annular flow path arranged below and connected to the hot gas nozzle; a gas inlet pipe that blows hot gas into the annular flow path; and guide vanes arranged at the outlet of the gas inlet pipe, which cause the hot gas introduced from the gas inlet pipe into the annular flow path to swirl in one direction, thereby causing the hot gas to be blown evenly from the hot gas nozzle in the circumferential direction.

[0005] Patent Document 1: Japanese Patent Application Publication No. 4-256449

[0006] The guide vanes at the outlet of the gas inlet pipe rectify the hot gas, but on the other hand, they also become a resistance to the flow of the hot gas, thus causing a pressure loss of the hot gas. Summary of the Invention

[0007] This disclosure was made in view of the above circumstances, and its purpose is to make the flow of gas rising in the mill housing in a vertical roller mill uniform in the circumferential direction while suppressing pressure loss.

[0008] To address the aforementioned issues, one embodiment of the vertical roller mill disclosed herein comprises: a rotating worktable that rotates about a worktable axis extending in a vertical direction; a crushing roller disposed on the upper surface of the rotating worktable; a separator disposed above the rotating worktable, having a classifying rotor that rotates about a rotor axis extending in the vertical direction, for classifying the crushed material transported by an airflow after being crushed by the rotating worktable and the crushing roller; a mill housing that houses the rotating worktable, the crushing roller, and the separator, and having an exhaust port disposed above the separator; an annular flow path that is circular and surrounds the outer periphery of the rotating worktable; at least one gas inlet pipe that blows hot gas having a velocity component in the tangential direction of the annular flow path toward a certain flow path cross-section of the annular flow path; and a hot gas nozzle that is circular and surrounds the outer periphery of the rotating worktable, for blowing the hot gas from the annular flow path away from the outer periphery of the rotating worktable.

[0009] According to this disclosure, in a vertical roller mill, the flow of gas rising within the mill casing can be homogenized circumferentially while suppressing pressure loss. Attached Figure Description

[0010] Figure 1 This is a diagram illustrating a schematic structure of a vertical roller mill according to one embodiment of the present disclosure.

[0011] Figure 2 This is a schematic top view of the annular flow path and gas inlet pipe.

[0012] Figure 3 This is a schematic top view showing a modified example of the layout of the gas inlet pipe, including an annular flow path and the gas inlet pipe itself.

[0013] Label Explanation

[0014] 1: Vertical roller mill; 2: Rotary worktable; 3: Crushing roller; 7: Mill housing; 9: Separator; 20: Worktable shaft; 73: Hot gas nozzle; 74: Gas inlet pipe; 74a: First gas inlet pipe; 74b: Second gas inlet pipe; 75: Annular flow path; 91: Stage rotor; 94: Rotor shaft. Detailed Implementation

[0015] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0016] [Simplified structure of vertical roller mill 1]

[0017] Figure 1 This is a diagram illustrating a schematic structure of a vertical roller mill 1 according to one embodiment of the present disclosure. Figure 1As shown, the vertical roller mill 1 has a rotating worktable 2, crushing rollers 3 rolling on the upper surface of the rotating worktable 2, and a separator 9 disposed above the rotating worktable 2. The rotating worktable 2, the multiple crushing rollers 3, and the separator 9 are covered by the mill housing 7.

[0018] The rotary table 2 is circular with a table axis 20 extending vertically as its center. The rotary table 2 is driven to rotate around the table axis 20 by a table drive unit 5. The table drive unit 5 includes a mill motor 51 and a reducer 52 that amplifies the rotational torque of the mill motor 51 and transmits it to the rotary table 2. Raw materials are supplied to the upper surface of the rotary table 2 via a raw material feed chute 8. The inlet of the raw material feed chute 8 is located outside the mill housing 7, and raw materials are metered into the inlet of the raw material feed chute 8 by a feeder 14.

[0019] A ring-shaped hot air nozzle 73 is provided between the outer periphery of the rotary table 2 and the mill housing 7, surrounding the outer periphery of the rotary table 2. The hot air nozzle 73 may have an annular opening surrounding the outer periphery of the rotary table 2, or it may have multiple openings arranged in a ring around the outer periphery of the rotary table 2. An annular flow path 75, communicating with the hot air nozzle 73, is provided on the outer periphery of the rotary table 2, below its upper surface. A gas inlet pipe 74, supplying hot air to the annular flow path 75, is connected to the annular flow path 75. The gas inlet pipe 74 is connected to a hot air source via piping or the like.

[0020] Multiple crushing rollers 3 are arranged at equal angular intervals on a circumferential track centered on the rotation axis of the rotary table 2. Figure 1 The example shows two of a plurality of crushing rollers 3. The plurality of crushing rollers 3 are elastically pressed onto the rotary table 2 by roller pressing devices 4 having a drive source such as a hydraulic cylinder.

[0021] A funnel-shaped internal cone 11 is disposed above the rotary table 2. The outlet of the internal cone 11 is located above the center of the rotary table 2. Inside the mill housing 7, a separator 9 is disposed above the internal cone 11.

[0022] The separator 9 classifies the pulverized material, which is transported along with hot air blown from the hot air nozzle 73, into fine powder and coarse powder. The separator 9 has a classifying rotor 91 consisting of multiple rotating blades arranged in a ring around a rotor shaft 94, guide vanes 92 arranged around the classifying rotor 91, and a separator drive device 93 that drives the classifying rotor 91 to rotate.

[0023] A mill outlet 71, serving as the exhaust port for the mill housing 7, is provided above the separator 9. An exhaust passage 31 is connected to the mill outlet 71. A collection device 33 is provided in the exhaust passage 31 to collect the pulverized material accompanying the mill exhaust. The collection device 33 can be, for example, a bag filter or a cyclone separator. Additionally, an exhaust fan 34 is provided in the exhaust passage 31. The flow rate of the mill exhaust can be adjusted by varying the rotational speed of this exhaust fan.

[0024] Next, the crushing operation of the vertical roller mill 1 with the above-described structure will be explained. The rotary table 2 rotates, and the multiple crushing rollers 3 roll on the rotary table 2 driven by the rotation of the rotary table 2. Moreover, when raw material is supplied to approximately the center of the rotary table 2 through the raw material feeding chute 8, the raw material moves towards the outer edge of the rotary table 2 by the centrifugal force driven by the rotation of the rotary table 2, and is bitten between the rotary table 2 and the crushing rollers 3 and crushed.

[0025] Hot air, blown from the hot air source through the gas inlet pipe 74 into the annular flow path 75, is blown up by the hot air nozzle 73. The pulverized material moves further towards the outer edge of the rotating table 2 due to centrifugal force, is dried by the hot air blowing around the rotating table 2, and is transported upwards by the airflow. Additionally, pulverized material, gravel, metal fragments, and other spillage not on the hot air flow fall from the outer periphery of the rotating table 2 due to centrifugal force and are recovered.

[0026] The pulverized material, rising within the mill casing 7 accompanied by hot air, is separated into coarse and fine particles by the separator 9. The fine particles separated by the separator 9 are conveyed to the mill outlet 71 by the airflow and flow out through the exhaust path 31. The fine particles flowing out of the exhaust path 31 are separated from the airflow by the collection device 33 and are recovered as product. On the other hand, the coarse particles separated by the separator 9 slide down in the inner cone 11 and return to the rotary table 2, where they are pulverized again along with the raw material.

[0027] [Structure of the annular flow path 75 and the gas inlet pipe 74]

[0028] Here, the structure of the annular flow path 75 and the gas inlet pipe 74 is described in detail. Figure 2 This is a schematic top view of the annular flow path 75 and the gas inlet pipe 74. (See attached image.) Figure 2As shown, an annular flow path 75 is formed between the mill housing 7 and the rotary table 2, forming a ring around the outer periphery of the rotary table 2. In other words, the annular flow path 75 is annular with the table axis 20 as its center. For ease of explanation, any position in the circumferential direction of the annular flow path 75 is set to 0°. At least one gas inlet pipe 74 is connected to the annular flow path 75 to blow hot gas into it. In the vertical roller mill 1 of this embodiment, two gas inlet pipes 74, a first gas inlet pipe 74a and a second gas inlet pipe 74b, are connected to the annular flow path 75.

[0029] The flow path section of the first gas inlet pipe 74a facing the 0° position of the annular flow path 75 blows hot gas parallel to the tangential direction T0 at the 0° position of the annular flow path 75 when viewed from above. Therefore, the outlet of the first gas inlet pipe 74a and its vicinity extend parallel to the tangential direction T0 when viewed from above.

[0030] The flow path section of the second gas inlet pipe 74b, facing the annular flow path 75 at a position of 180°, blows hot gas out parallel to the tangential direction T180 at the 180° position of the annular flow path 75 when viewed from above. Therefore, the outlet of the second gas inlet pipe 74b and its vicinity extend parallel to the tangential direction T180 when viewed from above.

[0031] The direction of hot gas blowing out from the first gas inlet pipe 74a (viewed from above) differs from that of the second gas inlet pipe 74b (viewed from above) by 180°, but both are in the same direction of rotation as the rotary table 2. Furthermore, the direction of hot gas blowing out from the first gas inlet pipe 74a and the second gas inlet pipe 74b (viewed from above) is the same as the direction of rotation of the stage rotor 91 of the separator 9.

[0032] When viewed from the side, the hot gas is blown out in a roughly horizontal or slightly upward direction from the horizontal. Thus, by adjusting the configuration and orientation of the gas inlet pipes 74, the direction of hot gas flow through the gas inlet pipes 74 can be controlled, thereby suppressing pressure loss of the hot gas compared to using louvers or guide vanes to adjust the flow direction.

[0033] Hot gas is blown into the annular flow path 75 from the first gas inlet pipe 74a and the second gas inlet pipe 74b, creating a swirling flow of hot gas within the annular flow path 75. The hot gas is blown into the annular flow path 75 from the first gas inlet pipe 74a and the second gas inlet pipe 74b in the same direction of rotation. Because the hot gas is blown into the annular flow path 75 in the direction of rotation, collisions with the walls forming the annular flow path 75 are reduced compared to the case where the hot gas is blown into the annular flow path 75 in the radial direction, thus suppressing pressure loss. Viewed from above, the rotation direction of the swirling flow within the annular flow path 75 is the same as the rotation direction of the rotary table 2. Furthermore, viewed from above, the rotation direction of the swirling flow within the annular flow path 75 is the same as the rotation direction of the stage rotor 91 of the separator 9.

[0034] The hot air within the annular flow path 75 becomes a laminar flow in the direction of rotation of the rotary table 2 and is blown out approximately evenly throughout the circumference from the hot air nozzle 73. The hot air blown out from the hot air nozzle 73, along with the pulverized material, swirls and rises within the mill housing 7, flowing into the separator 9. That is, an upward swirling flow is generated within the mill housing 7. The rotation direction of the upward swirling flow within the mill housing 7 is the same as the rotation direction of the rotary table 2. This upward swirling flow rectifyes the airflow within the mill housing 7, suppressing pressure loss. Furthermore, the rotation direction of the upward swirling flow within the mill housing 7 is the same as the rotation direction of the classifying rotor 91 of the separator 9, thereby causing the airflow to act more evenly on the separator 9 throughout the circumference. Thus, in the vertical roller mill 1, the airflow within the mill housing 7 is rectified, thereby suppressing pressure loss. Additionally, the rectified airflow acting on the separator 9 contributes to improving the classification performance of the separator 9.

[0035] Furthermore, in the vertical roller mill 1 of the above embodiment, hot gas is blown from the gas inlet pipe 74 into the annular flow path 75 at the 0° position parallel to the tangential direction T0. The hot gas blown out from the gas inlet pipe 74 has only a velocity component parallel to the tangential direction of the annular flow path 75 in the flow path cross-section of the target flow path, making it highly efficient. However, it is sufficient that the hot gas blown from the gas inlet pipe 74 into the annular flow path 75 only has a tangential component. For example, in... Figure 3 In the modified example shown, hot gas with a velocity component in the tangential direction Tα at position α° is blown in from the gas inlet pipe 74a toward the flow path section of the annular flow path 75. Additionally, hot gas with a velocity component in the tangential direction Tβ at position β° is blown in from the gas inlet pipe 74b toward the flow path section of the annular flow path 75. The hot gas blown out from these gas inlet pipes 74a and 74b also promotes the formation of a swirling flow in the annular flow path 75.

[0036] 〔Summarize〕

[0037] The vertical roller mill 1 of the first item of this disclosure includes: a rotary table 2 that rotates about a table shaft 20 extending in the vertical direction; a crushing roller 3 disposed on the upper surface of the rotary table 2; a separator 9 disposed above the rotary table 2, having a grading rotor 91 that rotates about a rotor shaft 94 extending in the vertical direction, for grading the crushed material transported by airflow after being crushed by the rotary table 2 and the crushing roller 3; a mill housing 7 that houses the rotary table 2, the crushing roller 3 and the separator 9, and has an exhaust port disposed above the separator 9; an annular flow path 75 that is annularly surrounding the outer periphery of the rotary table 2; at least one gas inlet pipe 74 that blows hot gas having a velocity component in the tangential direction of the annular flow path 75 toward a certain flow path section of the annular flow path 75; and a hot gas nozzle 73 that is annularly surrounding the outer periphery of the rotary table 2, for blowing the hot gas from the annular flow path 75 from the outer periphery of the rotary table 2.

[0038] The vertical roller mill 1 of the second item of this disclosure is based on the vertical roller mill 1 of the first item, wherein hot gas is blown out from the gas inlet pipe 74 in a top view parallel to the tangential direction of the annular flow path 75 in the flow path cross section.

[0039] In the vertical roller mill 1 of Projects 1 and 2, a swirling flow is generated in the annular flow path 75 by hot gas blown from the gas inlet pipe 74 into the annular flow path 75. This swirling flow in the annular flow path 75 suppresses pressure loss caused by collisions and eddies in the flow of hot gas within the annular flow path 75. Furthermore, the flow of hot gas within the annular flow path 75 is not formed by flow path components such as guide vanes or louvers, but rather by the flow of hot gas blown in from the gas inlet pipe 74. Therefore, pressure loss caused by collisions between hot gas and flow path components is eliminated.

[0040] Hot gas from the annular flow path 75 is blown out of the hot gas nozzle 73 in a uniform circumferential swirling flow, forming an upward swirling flow within the mill housing 7. This upward swirling flow within the mill housing 7 rectifys the airflow and suppresses pressure loss. Thus, according to the vertical roller mill 1 of this disclosure, the flow of rising gas within the mill housing 7 can be homogenized circumferentially while suppressing pressure loss. Furthermore, the rectified airflow acting on the separator 9 contributes to improving the classification performance of the separator 9.

[0041] The vertical roller mill 1 of the third item of this disclosure is based on the vertical roller mill 1 of the first or second item, wherein the direction of hot gas blowing out when viewed from above the gas inlet pipe 74 is the same as the direction of rotation of the rotary table 2.

[0042] As a result, the swirling direction of the hot air blown from the hot air nozzle 73 is the same as the rotation direction of the rotary table 2, and the rotation of the rotary table 2 promotes the flow of the rising swirling flow generated in the mill housing 7.

[0043] The vertical roller mill 1 of the fourth item of this disclosure is based on any one of the vertical roller mills 1 of items 1 to 3, wherein the direction of hot gas blowing out when viewed from above the gas inlet pipe 74 is the same as the direction of rotation of the grading rotor 91.

[0044] As a result, the upward swirling flow generated within the mill housing 7 rotates in the same direction as the classifying rotor 91, thus reducing the circumferential deviation in the flow of gas into the separator 9. By homogenizing the flow of the pulverized material accompanying the flow into the separator 9 in the circumferential direction, the classifying efficiency of the classifying rotor 91 is improved.

[0045] The vertical roller mill 1 of the fifth item of this disclosure is a vertical roller mill 1 according to any one of the items 1 to 4, wherein at least one gas inlet pipe 74 includes a first gas inlet pipe 74a and a second gas inlet pipe 74b, and the direction of hot gas blowing out of the first gas inlet pipe 74a is 180° different from the direction of hot gas blowing out of the second gas inlet pipe 74b.

[0046] By blowing hot air into the annular flow path 75 from multiple locations in the same direction of rotation, a stable swirling flow is generated in the annular flow path 75, and the collision of the blown hot air flow is suppressed.

[0047] The foregoing discussion of this disclosure is for illustrative purposes and is not intended to limit this disclosure to the manner disclosed in this specification. For example, in the foregoing detailed description, various features of this disclosure are summarized into one embodiment for the purpose of rationalizing this disclosure, but several of the multiple features may also be combined. In addition, the multiple features included in this disclosure may also be combined with alternative embodiments, structures, or methods other than those discussed above.

Claims

1. A vertical roller mill, comprising: A rotary table that rotates around a table axis extending vertically. A crushing roller is disposed on the upper surface of the rotary table; A separator, which is disposed above the rotary table, has a grading rotor that rotates around a rotor shaft extending in the vertical direction, and grades the pulverized material that has been pulverized by the rotary table and the pulverizing roller and is conveyed by the airflow. The mill housing houses the rotary table, the crushing roller, and the separator, and has an exhaust port disposed above the separator; The annular flow path is in the shape of a ring surrounding the outer periphery of the rotary table; At least one gas inlet pipe blows hot gas with a velocity component in the tangential direction of the annular flow path toward a certain cross-section of the annular flow path; and A hot air nozzle, which is annular in shape surrounding the outer periphery of the rotary table, blows the hot air from the outer periphery of the rotary table through the annular flow path.

2. The vertical roller mill according to claim 1, wherein, The gas inlet pipe blows out hot gas parallel to the tangent direction of the annular flow path in the flow path cross-section when viewed from above.

3. The vertical roller mill according to claim 1 or 2, wherein, When viewed from above, the direction in which the hot gas is blown out of the gas inlet pipe is the same as the direction of rotation of the rotary worktable.

4. The vertical roller mill according to claim 1 or 2, wherein, When viewed from above, the direction in which the hot gas is blown out is the same as the direction of rotation of the staged rotor.

5. The vertical roller mill according to claim 1 or 2, wherein, The at least one gas inlet pipe includes a first gas inlet pipe and a second gas inlet pipe, wherein the direction of hot gas blowing out of the first gas inlet pipe is 180° different from the direction of hot gas blowing out of the second gas inlet pipe.

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