Vertical roller mill

Abstract

In a vertical roller mill, the flow of gas rising within the mill casing is made uniform in the circumferential direction while suppressing pressure loss. [Solution] The vertical roller mill comprises a rotary table, a grinding roller positioned on the upper surface of the rotary table, a separator positioned above the rotary table and having a classifying rotor for classifying the pulverized material that has been air-conveyed after being ground by the rotary table and grinding roller, a mill casing housing the rotary table, grinding roller, and separator and having an exhaust port positioned above the separator, an annular flow channel surrounding the outer circumference of the rotary table, at least one gas introduction duct blowing out hot gas having a velocity component in the tangential direction of the annular flow channel at a certain cross-section of the annular flow channel, and a hot gas nozzle that forms an annular shape surrounding the outer circumference of the rotary table and blows the hot gas of the annular flow channel upward from the outer circumference of the rotary table.

Description

Technical Field

[0001] The present disclosure relates to a vertical roller mill provided with a separator.

Background Art

[0002] Conventionally, vertical roller mills have been used for crushing solid fuels such as coal and for crushing cement raw materials such as limestone and clay. Hereinafter, the material to be crushed in the vertical roller mill is referred to as a raw material, and the crushed raw material is referred to as a crushed product. Some vertical roller mills are provided with a separator for classifying the crushed product to adjust the product particle size.

[0003] The vertical roller mill includes a rotating table and a crushing roller elastically pressed onto the rotating table, and the raw material is bitten between the rotating table and the crushing roller and crushed. The crushed product moves toward the edge of the rotating table, rises in the mill casing along with the hot gas blown up from the periphery of the rotating table, is classified into fine powder and coarse powder by the separator, the fine powder is discharged from the discharge port at the upper part of the mill casing together with the gas, and the coarse powder is crushed again together with the raw material. In order to improve the classification efficiency of the separator, it is preferable that the airflow accompanied by the crushed product flows into the separator without bias.

[0004] <00000!5>Therefore, in the vertical roller mill of Patent Document 1, an annular annular flow path disposed below the hot gas nozzle and communicated with the hot gas nozzle, a gas introduction duct for blowing hot gas into the annular flow path, and a guide disposed at the duct outlet of the gas introduction duct are provided. By swirling the hot gas introduced from the gas introduction duct into the annular flow path in one direction by the action of the guide vane, the hot gas blows up uniformly in the circumferential direction from the hot gas nozzle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Guide vanes placed at the duct outlet of a gas introduction duct straighten the flow of hot gas, but they also create resistance to the flow of hot gas, resulting in a pressure loss of the hot gas.

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

[0008] To solve the above problems, a vertical roller mill according to one aspect of this disclosure is provided. A rotary table that rotates around a table axis that extends vertically, A crushing roller positioned on the upper surface of the aforementioned rotating table, A separator is positioned above the aforementioned rotating table and has a classification rotor that rotates around a rotor shaft extending in the vertical direction, and classifies the pulverized material that has been pulverized by the rotating table and the pulverizing rollers and then conveyed by airflow, A mill casing housing the rotary table, the grinding roller, and the separator, and having an exhaust port positioned above the separator, An annular channel forming a ring shape surrounding the outer circumference of the aforementioned rotating table, A gas introduction duct that blows out a hot gas having a velocity component in the tangential direction of the annular flow channel at a certain cross-section of the annular flow channel, The system includes a hot gas nozzle that has an annular shape surrounding the outer circumference of the rotary table and blows the hot gas from the annular flow path upward from the outer circumference of the rotary table. [Effects of the Invention]

[0009] According to this disclosure, in a vertical roller mill, the flow of gas rising within the mill casing can be made uniform in the circumferential direction while suppressing pressure loss. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a schematic configuration of a vertical roller mill according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic plan view of the annular flow path and gas introduction duct. [Figure 3] Figure 3 is a schematic plan view of an annular flow path and a gas introduction duct, showing a modified layout of the gas introduction duct. [Modes for carrying out the invention]

[0011] Next, embodiments of the present invention will be described with reference to the drawings.

[0012] [Outline configuration of vertical roller mill 1] Figure 1 is a schematic diagram of a vertical roller mill 1 according to one embodiment of the present disclosure. As shown in Figure 1, the vertical roller mill 1 comprises a rotary table 2, grinding rollers 3 that roll on the upper surface of the rotary table 2, and a separator 9 positioned above the rotary table 2. The rotary table 2, the plurality of grinding rollers 3, and the separator 9 are covered by a mill casing 7.

[0013] The rotary table 2 has a circular shape centered on a table axis 20 that extends in the vertical direction. The rotary table 2 is rotationally driven around the table axis 20 by a table drive device 5. The table drive device 5 includes a mill motor 51 and a reduction gear 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 through a raw material input chute 8. The inlet of the raw material input chute 8 is located outside the mill casing 7, and raw materials are supplied quantitatively to the inlet of the raw material input chute 8 by a feeder 14.

[0014] An annular hot gas nozzle 73 is provided between the outer edge of the rotary table 2 and the milk casing 7, surrounding the outer circumference of the rotary table 2. The hot gas nozzle 73 may have an annular opening surrounding the outer circumference of the rotary table 2, or it may have multiple openings arranged in an annular pattern on the outer circumference of the rotary table 2. An annular flow path 75 is provided on the outer circumference of the rotary table 2, below the upper surface of the rotary table 2, and is in communication with the hot gas nozzle 73. A gas introduction duct 74 is connected to the annular flow path 75 to supply hot gas to the annular flow path 75. The gas introduction duct 74 is connected to a hot gas source via piping or the like.

[0015] Multiple grinding rollers 3 are arranged at equal angular intervals on a circular orbit centered on the rotation axis of the rotary table 2. Figure 1 shows two of the multiple grinding rollers 3 as an example. Each of the multiple grinding rollers 3 is elastically pressed against the rotary table 2 by a roller pressing device 4 equipped with a drive source such as a hydraulic cylinder.

[0016] An inner cone 11, which has a funnel shape, is positioned above the rotating table 2. The discharge port of the inner cone 11 is located above the center of the rotating table 2. A separator 9 is positioned above the inner cone 11 within the milk casing 7.

[0017] The separator 9 separates the pulverized material, which has been transported along with the hot gas blown up from the hot gas nozzle 73, into fine powder and coarse powder. The separator 9 comprises a classification rotor 91 consisting of multiple rotating blades arranged in an annular shape around a rotor shaft 94, guide vanes 92 arranged around the classification rotor 91, and a separator drive device 93 that rotates the classification rotor 91.

[0018] Above the separator 9, there is provided a mill outlet 71 which is an exhaust port of the mill casing 7. An exhaust passage 31 is connected to the mill outlet 71. A collecting device 33 for collecting pulverized materials entrained in the mill exhaust is provided in the exhaust passage 31. The collecting device 33 may be, for example, a bag filter or a cyclone. Further, an exhaust fan 34 is provided in the exhaust passage 31. The flow rate of the mill exhaust can be adjusted by changing the rotational speed of this exhaust fan.

[0019] Subsequently, the pulverizing operation of the vertical roller mill 1 configured as described above will be described. The rotary table 2 is rotating, and the plurality of pulverizing rollers 3 are rolling on the rotary table 2 following the rotation of the rotary table 2. When raw materials are supplied to substantially the center of the rotary table 2 through the raw material input chute 8, the raw materials move toward the outer edge of the rotary table 2 by the centrifugal force accompanying the rotational drive of the rotary table 2, and are caught between the rotary table 2 and the pulverizing rollers 3 and pulverized.

[0020] The hot gas blown into the annular flow path 75 from the hot gas source through the gas introduction duct 74 is blowing up from the hot gas nozzle 73. The pulverized materials move further toward the outer edge of the rotary table 2 by the centrifugal force, and are dried by the hot gas blowing up around the rotary table 2 and conveyed upward by the air flow. Note that the spillage such as pulverized materials that do not ride on the air flow of the hot gas, gravel, and metal pieces fall from the outer peripheral edge of the rotary table 2 by the centrifugal force and are recovered.

[0021] The pulverized materials that have risen in the mill casing 7 along with the hot gas are classified into coarse particles and fine particles by the separator 9. The fine particles classified by the separator 9 are conveyed to the mill outlet 71 by the air flow and flow out from the mill outlet 71 to the exhaust passage 31. The fine particles that have flowed out to the exhaust passage 31 are separated from the air flow by the collecting device 33 and recovered as products. On the other hand, the coarse particles classified by the separator 9 slide down the inner cone 11 and are returned onto the rotary table 2 and pulverized again together with the raw materials.

[0022] 〔Configuration of the annular flow path 75 and the gas introduction duct 74〕 Here, the configuration of the annular channel 75 and the gas introduction duct 74 will be described in detail. Figure 2 is a schematic plan view of the annular channel 75 and the gas introduction duct 74. As shown in Figure 2, the annular channel 75 is formed between the mill casing 7 and the rotary table 2 and has an annular shape surrounding the outer circumference of the rotary table 2. In other words, the annular channel 75 has an annular shape centered on the table axis 20. For the sake of explanation, any position in the circumferential direction of the annular channel 75 will be designated as the 0° position. At least one gas introduction duct 74 is connected to the annular channel 75 for blowing hot gas into the annular channel 75. In the vertical roller mill 1 according to this embodiment, two gas introduction ducts 74, a first gas introduction duct 74a and a second gas introduction duct 74b, are connected to the annular channel 75.

[0023] The first gas introduction duct 74a blows out hot gas toward the cross-section of the annular flow path 75 at the 0° position, parallel to the tangential direction T0 at the 0° position of the annular flow path 75 in a plan view. For this reason, the outlet of the first gas introduction duct 74a and its vicinity extend parallel to the tangential direction T0 in a plan view.

[0024] The second gas introduction duct 74b blows out hot gas toward the cross-section of the annular flow path 75 at the 180° position, parallel to the tangential direction T180 at the 180° position of the annular flow path 75 in a plan view. For this reason, the outlet of the second gas introduction duct 74b and its vicinity extend parallel to the tangential direction T180 in a plan view.

[0025] The direction of hot gas discharge in the plan view of the first gas introduction duct 74a and the direction of hot gas discharge in the plan view of the second gas introduction duct 74b differ by 180°, but both are the same as the rotation direction of the rotary table 2. In addition, the direction of hot gas discharge in the plan view of the first gas introduction duct 74a and the second gas introduction duct 74b is the same as the rotation direction of the classification rotor 91 of the separator 9.

[0026] In a side view, the direction of hot gas discharge from the first gas introduction duct 74a and the second gas introduction duct 74b is approximately horizontal or slightly upward from horizontal. In this way, the direction of hot gas discharge from the gas introduction duct 74 is adjusted by the arrangement and orientation of the gas introduction duct 74, so that the pressure loss of the hot gas can be suppressed compared to cases where the discharge direction is adjusted using louvers or guide vanes.

[0027] The hot gas blown into the annular channel 75 from the first gas introduction duct 74a and the second gas introduction duct 74b creates a swirling flow of hot gas in the annular channel 75. The hot gas is blown into the annular channel 75 from the first gas introduction duct 74a and the second gas introduction duct 74b in the same direction of rotation. Since the hot gas is blown into the annular channel 75 in the direction of rotation, collisions with the walls forming the annular channel 75 are reduced and pressure loss is suppressed compared to when the hot gas is blown into the annular channel 75 in the radial direction. In a plan view, the direction of rotation of the swirling flow in the annular channel 75 is the same as the direction of rotation of the rotary table 2. Also, in a plan view, the direction of rotation of the swirling flow in the annular channel 75 is the same as the direction of rotation of the classification rotor 91 of the separator 9.

[0028] The hot gas in the annular flow path 75 becomes a laminar flow in the direction of rotation of the rotary table 2 and is blown out almost uniformly from the hot gas nozzle 73 in the circumferential direction. The hot gas blown out from the hot gas nozzle 73 rises while swirling inside the mill casing 7, accompanied by the pulverized material, and flows into the separator 9. In other words, an upward swirling flow is generated inside the mill casing 7. The direction of rotation of the upward swirling flow inside the mill casing 7 is the same as the direction of rotation of the rotary table 2. The upward swirling flow rectifies the airflow inside the mill casing 7 and suppresses the pressure loss of the airflow. Furthermore, the direction of rotation of the upward swirling flow inside the mill casing 7 is the same as the direction of rotation of the classification rotor 91 of the separator 9, so that the airflow acts more uniformly on the separator 9 in the circumferential direction. In this way, in the vertical roller mill 1, the pressure loss of the airflow is suppressed by rectifying the airflow inside the mill casing 7. Furthermore, the rectified airflow acts on the separator 9, contributing to an improvement in the classification performance of the separator 9.

[0029] In the vertical roller mill 1 according to the above embodiment, hot gas is blown from the gas introduction duct 74 to the 0° position of the annular flow path 75 parallel to the tangential direction T0. It is efficient for the hot gas blown out from the gas introduction duct 74 to have only a velocity component parallel to the tangential direction of the annular flow path 75 at the flow path cross-section of the blowing target. However, the hot gas blown from the gas introduction duct 74 into the annular flow path 75 only needs to have a tangential component. For example, in the modified example shown in Figure 3, hot gas having a velocity component in the tangential direction Tα at the α° position is blown from the gas introduction duct 74a toward the flow path cross-section at the α° position of the annular flow path 75. Also, hot gas having a velocity component in the tangential direction Tβ at the β° position is blown from the gas introduction duct 74b toward the flow path cross-section at the β° position of the annular flow path 75. The formation of a swirling flow in the annular flow path 75 can also be promoted by the hot gas blown out from such gas introduction ducts 74a and 74b.

[0030] [Summary] The vertical roller mill 1 relating to item 1 of this disclosure is A rotary table 2 that rotates around a table axis 20 that extends in the vertical direction, A crushing roller 3 is positioned on the upper surface of the rotating table 2, A separator 9 is positioned above the rotary table 2 and has a classification rotor 91 that rotates around a rotor shaft 94 that extends in the vertical direction, and classifies the pulverized material that has been pulverized by the rotary table 2 and the pulverizing rollers 3 and then conveyed by airflow, A mill casing 7 houses a rotating table 2, a grinding roller 3, and a separator 9, and has an exhaust port located above the separator 9. An annular channel 75 that forms a ring shape surrounding the outer circumference of the rotary table 2, A gas introduction duct 74 blows hot gas having a velocity component tangential to the annular channel 75 at a certain channel cross-section toward the annular channel 75, The system includes a hot gas nozzle 73 that has an annular shape surrounding the outer circumference of the rotary table 2 and blows hot gas from the annular flow path 75 upward from the outer circumference of the rotary table 2.

[0031] The vertical roller mill 1 according to the second item of this disclosure is the same as the vertical roller mill 1 according to the first item, wherein the gas introduction duct 74 blows out hot gas parallel to the tangential direction of the annular flow path 75 in the cross-section of the flow path and in a plan view.

[0032] In the vertical roller mill 1 relating to the first and second items, a swirling flow is generated in the annular channel 75 by the hot gas blown from the gas introduction duct 74 into the annular channel 75. The swirling flow formed in the annular channel 75 suppresses pressure loss due to collisions and vortex generation of the hot gas flow within the annular channel 75. Furthermore, the hot gas flow within the annular channel 75 is formed by the hot gas flow blown in from the gas introduction duct 74, rather than by flow path members such as guide vanes or louvers. Therefore, there is no pressure loss of hot gas caused by the hot gas colliding with flow path members.

[0033] The hot gas in the annular channel 75 is blown out from the hot gas nozzle 73 as a uniform swirling flow in the circumferential direction, forming an upward swirling flow within the mill casing 7. The upward swirling flow formed within the mill casing 7 straightens the airflow within the mill casing 7, suppressing pressure loss in the airflow. Thus, according to the vertical roller mill 1 of this disclosure, the gas flow rising within the mill casing 7 can be made uniform in the circumferential direction while suppressing pressure loss. Furthermore, the straightened airflow acts on the separator 9, contributing to an improvement in the classification performance of the separator 9.

[0034] The vertical roller mill 1 relating to item 3 of this disclosure is a vertical roller mill 1 relating to item 1 or 2, wherein the direction of discharge of hot gas in a plan view of the gas introduction duct 74 is the same as the direction of rotation of the rotary table 2.

[0035] As a result, the swirling direction of the hot gas blown up from the hot gas nozzle 73 and the rotation direction of the rotary table 2 are in the same direction, and the upward swirling flow generated inside the milk casing 7 is promoted by the rotation of the rotary table 2.

[0036] The vertical roller mill 1 relating to item 4 of this disclosure is a vertical roller mill 1 relating to any of items 1 to 3, wherein the direction of discharge of the hot gas in a plan view of the gas introduction duct 74 is the same as the rotation direction of the classification rotor 91.

[0037] As a result, the direction of rotation of the rising swirling flow generated within the mill casing 7 and the direction of rotation of the classification rotor 91 are the same, reducing the circumferential bias of the gas flow into the separator 9. By making the gas flow containing the pulverized material into the separator 9 more uniform in the circumferential direction, the classification efficiency of the classification rotor 91 is increased.

[0038] The vertical roller mill 1 relating to item 5 of this disclosure is a vertical roller mill 1 relating to any of items 1 to 4, wherein at least one gas introduction duct 74 includes a first gas introduction duct 74a and a second gas introduction duct 74b, and the direction of hot gas discharge from the first gas introduction duct 74a and the direction of hot gas discharge from the second gas introduction duct 74b are 180° apart.

[0039] In this way, by injecting hot gas into the annular channel 75 from multiple locations in the same direction of rotation, a stable swirling flow is generated in the annular channel 75, and collisions between the injected hot gas flows are suppressed.

[0040] The discussions of this disclosure described above are presented for illustrative and explanatory purposes only and are not intended to limit the disclosure to the forms disclosed herein. For example, in the detailed description above, various features of the disclosure are grouped into a single embodiment for the purpose of streamlining the disclosure, but some of the features may be combined. Also, some of the features included in this disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above. [Explanation of symbols]

[0041] 1: Vertical roller mill 2: Rotating table 3: Crushing roller 7: Mill casing 9: Separator 20: Table axis 73: Hot gas nozzle 74: Gas introduction duct 74a: First gas introduction duct 74b: Second gas introduction duct 75: Circular channel 91: Classification rotor 94: Rotor shaft

Claims

1. A rotary table that rotates around a table axis that extends vertically, A crushing roller positioned on the upper surface of the aforementioned rotating table, A separator is positioned above the aforementioned rotating table and has a classification rotor that rotates around a rotor shaft extending in the vertical direction, and classifies the pulverized material that has been pulverized by the rotating table and the pulverizing rollers and then conveyed by airflow, A mill casing housing the rotary table, the grinding roller, and the separator, and having an exhaust port positioned above the separator, An annular channel forming a ring shape surrounding the outer circumference of the aforementioned rotating table, A gas introduction duct that blows out a hot gas having a velocity component in the tangential direction of the annular flow path in the cross-section of the annular flow path toward a certain cross-section of the annular flow path, The rotating table comprises a hot gas nozzle that forms an annular shape surrounding the outer circumference of the rotating table and blows the hot gas from the annular flow path upward from the outer circumference of the rotating table. Vertical roller mill.

2. The gas introduction duct blows out the hot gas parallel to the tangential direction of the annular flow path in the cross-section of the flow path and in a plan view. The vertical roller mill according to claim 1.

3. In a plan view of the gas introduction duct, the direction of discharge of the hot gas is the same as the direction of rotation of the rotary table. A vertical roller mill according to claim 1 or 2.

4. In a plan view of the gas introduction duct, the direction of discharge of the hot gas is the same as the rotation direction of the classification rotor. A vertical roller mill according to claim 1 or 2.

5. The at least one gas introduction duct includes a first gas introduction duct and a second gas introduction duct, wherein the direction of discharge of the hot gas from the first gas introduction duct and the direction of discharge of the hot gas from the second gas introduction duct differ by 180°. A vertical roller mill according to claim 1 or 2.

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