JP3096071B2 - Roller mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller mill and, more particularly, to a roller mill capable of greatly reducing the vibration of the mill due to the sliding of a crushing roller and reducing the minimum load of an operable mill.

[0002]

2. Description of the Related Art In coal-fired boilers, low-pollution combustion (NO
x and reduction of unburned content in ash) and wide-area load operation technology have been promoted, and accordingly, pulverized coal mills (mills) have also been required to have high performance.

[0003] As one type of mill for finely pulverizing lump such as coal, cement raw material or new raw material, a vertical roller mill for pulverizing with a rotating table and a plurality of rollers has been widely used. We are solidifying our position as one of the representative models.

A mill of this type is, for example, shown in FIG. 1, a substantially disk-shaped rotary table 3 which is driven by an electric motor and rotates at a low speed through a speed reducer under a cylindrical housing 14 and the table. Section U provided on the outer periphery of
A plurality of crushing rollers 4 which are rotated by being pressurized by a hydraulic pressure or a spring or the like at a position equally divided in a circumferential direction on an upper surface of the crushing race 19 formed of a letter-shaped ring groove are provided. These crushing rollers rotate by frictional force generated between the crushing roller and the raw material compressed between the rotary table. The raw material 1 to be crushed supplied from the chute 2 to the center of the rotary table moves to the outer periphery of the rotary table by drawing a spiral trajectory by centrifugal force on the rotary table,
It is crushed between the crushing race surface of the rotary table and the crushing roller. Hot air 17 is guided to the lower part of the mill housing 14 through a duct, and the hot air is blown up from an air throat (throat ring) 25 between the rotary table and the housing. The granules produced by the pulverization fall from the coarse ones by gravity (primary classification) and are pulverized again in the pulverization section. The slightly fine powder that has passed through the primary classifier is classified again by a cyclone separator or a rotary separator (rotary classifier) 22 provided on the upper part of the housing. Fine powder smaller than a predetermined particle size is conveyed by an air stream, and is sent to a pulverized coal burner or a pulverized coal storage bin in a boiler. Coarse particles having a predetermined particle size or more that have not passed through the classifier fall onto the table by gravity, are pulverized again together with the coarse particles returned by the primary classification and the raw material (bulk coal) just supplied into the mill. You. In this way, pulverization is repeated in the mill, and product fine powder is generated.

[0005]

When the roller mill is operated at a low load, a problem in reducing the load is vibration of the mill. Although this vibration phenomenon is complicated and a detailed mechanism has not been clarified, it is said that it is a kind of friction vibration (stick-slip motion) caused by sliding of the powder layer and the roller. The type of vibration can be considered as a type of self-excited vibration because the excitation source cannot be clearly identified. In ordinary coal, as shown in FIG. 15, this vibration becomes intense during low-load operation (coal hold-up in the mill is small). However, depending on the type of coal, this vibration may occur even at a considerably high load. The pulverizability of coal which easily causes such vibrations varies from good to fairly bad. Therefore, it is generally difficult to predict in advance whether or not vibration is likely to occur only by the pulverizability of coal.

FIG. 18 is a sectional view showing a supporting structure of a conventional pulverizing roller. In this type of roller mill, a crushing roller 1801 is supported via a roller bracket 1802 so as to be able to swing around a roller pivot 1805 as a support shaft. This swinging function is very important, and when the raw material is supplied into the mill at once at the start of the mill or the crushing roller 1801 collides with foreign matter, the crushing roller 1801 can avoid the impact by shaking the head. it can. When the crushing roller 1801 is worn, the swinging function also has a function of automatically and appropriately finding an appropriate pressing position (the positional relationship between the crushing roller 1801 and the crushing race 1812). Generally, at the time of high-load pulverization, the pulverizing roller 1801 hardly shakes its head. As described above, when the crushing roller 1801 vigorously bites the raw material at the time of starting the mill or when the load is increased, the crushing roller 1801 swings, but in this swinging operation, the three crushing rollers are synchronized. do not do.
At this time, the mill vibrates.
Since the frequency 801 is not synchronized, there is no dominant frequency and the frequency distribution is broad so-called forced vibration, and does not hinder the operation of the mill except in extreme cases.

On the other hand, when the rollers vibrate violently by self-excitation, as shown in FIG. 16, the roller pivot 1805 slightly lowers (.alpha.), And the three crushing rollers 1801 are simultaneously laterally outwardly shifted (.beta.). ), And then vibrates up and down as shown in FIG. The three grinding rollers oscillate vertically (in phase) together in synchronization. The grasp of such a vibration phenomenon is based on the result of the inventors installing a displacement meter or an accelerometer in a roller mill of a pilot scale and measuring the vibration at the time of vibration.

As described above, in order to suppress the vibration of the mill by devising the hardware of the crushing unit, it is important to prevent the movement (in-phase movement) of the three crushing rollers being synchronized. The object of the present invention is to prevent the crushing roller from shaking its head or vibrating up and down synchronously based on the above-mentioned concept, and to be able to operate in a wide area load or a high coal type without causing vibration. To provide a roller mill.

[0009]

According to a first aspect of the present invention, there is provided a rotary table rotating in a horizontal plane below a mill housing, a grinding race provided on an outer peripheral portion of an upper surface of the rotary table, and
A plurality of crushing rollers that are placed on the race and pressed and rotated, a roller bracket that rotatably supports each crushing roller, and a roller pivot that supports each of the roller brackets so that they can pendulum move, In a roller mill for crushing raw materials to be crushed by a crushing roller and a crushing race, an attachment angle (θ) of at least one crushing roller with respect to a vertical line is configured to be different from the mounting angle of another crushing roller. Related to roller mill.

[0010] The second invention is the above-mentioned first invention, wherein:
The present invention relates to a roller mill, wherein each of the crushing rollers has a different mounting angle with respect to a vertical line.

[0011] A third invention relates to the roller mill according to the first or second invention, wherein the difference in the mounting angle of the crushing rollers is within 2 degrees.

According to a fourth aspect of the present invention, there is provided a rotary table rotating in a horizontal plane below a mill housing, a grinding race provided on an outer peripheral portion of an upper surface of the rotary table, and a plurality of rotary members mounted on the race and rotated by being pressed. In a roller mill that has a roller bracket that rotatably supports each of the pulverizing rollers, and a roller pivot that supports each of the roller brackets so that they can pendulum move, a pulverizing raw material is pulverized by a pulverizing roller and a pulverizing race. An extension of the grinding surface is provided on the outer side in the thickness direction of the grinding roller, and the radius of curvature and the center of curvature of the extension are matched with those of the grinding surface, and the at least one grinding roller has
Change the length of the extension roller in the circumferential (rotation) direction
The present invention relates to a roller mill having a different length from the roller.

[0013]

[0014]

[Function] When the roller mill starts to vibrate, the head is always shaken so that the grinding roller is shifted sideways. In other words, at the boundary between the pulverizing roller and the compressed powder layer or inside the compressed powder layer,
This results in lateral slippage.

If the angle of inclination (at the time of initial setting) of each crushing roller in the same mill is made different, the oscillating angle at the time of occurrence of a lateral shift differs for each crushing roller. At this time, vibrations are generated, but they are forced vibrations and attenuate. In this way, it is possible to prevent the crushing rollers from moving sideways synchronously (in the same phase) and vibrating up and down.

On the other hand, the crushing curved surface extension of the crushing roller strongly compresses the powder layer on the outer side of the crushing race (on the side of the mill housing). As a result, a strong resistance is generated in the swing direction of the grinding roller. Again,
Vibration occurs, but does not increase because the vibration phase of each roller is shifted and the movement is canceled. This makes it possible to prevent sudden sideways movement of the crushing roller, which is a sign of vibration. If the length of the extension of the crushing curved surface (circumferential direction of the crushing roller) is different for each crushing roller, the action interval (period) of the drag against the lateral displacement is set for each crushing roller
And the operating time will be different. By the action as described above, grinding rollers, it can prevent the movement that it causes a lateral displacement (in phase) synchronously develops the self-excited vibration. In the unlikely event that one or two crushing rollers cause an in-phase lateral movement by some trigger, the above-mentioned operation prevents all the crushing rollers from growing into intense self-excited vibrations synchronized with each other.

By combining the two means described above, that is, the inclination angle of the crushing roller and the structure of the crushing curved surface extending portion of the crushing roller, the movement of the crushing roller synchronously laterally displaced by the synergistic action is substantially suppressed. It becomes possible. When the crushing roller vibrates, it is premised that the crushing roller is caused to move laterally. Therefore, it is possible to prevent the vibration by using the above-described means according to the present invention.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the present invention relates to a crushing section of a mill centered on a crushing roller and a roller bracket, which will be described first.

As shown in FIG. 2, the roller mill of the present invention comprises a roller shaft 202 of a crushing roller 201.
Are supported by the roller bracket 205.
The roller bracket is bent at a specific inclination angle, and a roller pivot 207 is inserted through a pivot box 206 above the roller bracket. The roller pivot 207 is a fulcrum of the pendulum movement of the crushing roller 201 and a transmission point of a load applied from the spring 210 contracted by a tension rod (not shown). In the roller mill according to this embodiment, three crushing rollers are provided. As shown in this figure, these grinding rollers rotate at a specific inclination angle while strongly pressing the compressed powder layer 219 on the grinding race 215. The inclination angle of the grinding rollers, bending angle of the roller bracket both equal, referred as the slope angle in this figure, represented by the symbol of theta _1. In this embodiment, the inclination angle is changed for each grinding roller.
Theta ₁ of Figure 2 is the smallest, grinding roller theta ₃ shown in FIG. 4 is a maximum, the magnitude theta ₂ of the milling roller in FIG. 3 corresponds to these intermediate. That is, the relationship is set as θ ₁ <θ ₂ <θ ₃ . The standard θ ₂ is about 15 °, and θ ₂ and θ
₁ or θ ₂ and θ ₃ are different so that both are within 2 °. I mean

[0020]

(Equation 1)
θ ₂ −θ ₁ ≦ 2 °

[0021]

## EQU2 ## The inclination angle is set based on θ ₃ −θ ₂ ≦ 2 °. This was measured using a small test mill to measure torque fluctuations (idle rotation), and set as a range in which the fluctuations were small. If the difference between the inclination angles θ is too large, for example, if the difference is increased to near 5 °, the rotation of the grinding roller becomes unstable, causing unbalanced vibration, which is one type of so-called forced vibration.

As shown in FIG. 5A, in the pulverizing roller according to the present invention, a part of the pulverizing curved surface 503 is extended outward (toward the mill housing). Extension 50 of this crushed curved surface
4 is the center of curvature 0 and the radius of curvature γ in the cross section of the roller in the width direction.
₀ is the same as the crushed curved surface. Grinding roller 5
The angle α of the pulverized curved surface with respect to the cross-sectional center axis 502 of 01 is
The extension 504 is set to be about 30% larger. Also, the height of the extension of the grinding surface is determined by the grinding roller 5.
It is about 1.25γ ₀ from the lowest point of 01. The shape of the extension of the grinding surface on the thickness direction cross-sectional view of the grinding roller is
Equal to three grinding rollers.

FIG. 5B schematically shows a state in which the crushing roller 501 moves like a pendulum. The extension portion 504 of the crushing curved surface extends slightly along the outer peripheral end of the crushing ring 506 (there is no metal touch at this point in idle rotation. If there is a powder layer, the powder layer is compressed here). 506 is set, and here the crush roller 5
01 receives drag from the powder layer. Extension 504 of grinding surface
With respect to the circumferential (rotation) direction of the crushing roller 501,
As shown in FIGS. 6 to 8, it can be provided partially.
The crushing roller 201 shown in FIG.
The length Lα of 1b is the shortest and is about 1/6 of the circumference, and is combined with the roller bracket 205 having the smallest inclination angle (θ ₁ ) (FIG. 2). Grinding roller 301 shown in FIG.
Is the L?, Is about 1/3 of the circumference, is combined with the roller bracket 305 of the tilt angle theta ₂ (Fig. 3). FIG. 8 shows an example in which the extended portion of the crushed curved surface is the longest, and Lγ extends to approximately half of the circumference. This crushing roller 401
Is the roller bracket 4 with the largest inclination angle (θ ₃ )
05 (FIG. 4). FIG. 2 shows the combination θ ₁ +
The crushing roller showing Lα has a crushing portion structure in which the inclination angle of the roller is the minimum and the extension 201b of the crushing curved surface is short, so that the pendulum movement to the outside is most easily performed. On the other hand, in the combination of θ ₃ + Lγ as shown in FIG. 4, the crushing roller 401 is pressed to the outside of the crushing race 415 in advance, so that the pendulum does not easily move outward.
Conversely, the crushing roller is easily moved inward (toward the center axis of the mill), but in this case, the phase is shifted by 180 ° from the crushing roller shown in FIG. That is, the phase is shifted most greatly.

Although the order of the description has been reversed, the overall configuration (FIG. 1) of the roller mill equipped with the crushing roller and the roller bracket according to the present invention will now be described.

The raw material to be pulverized 1 is supplied from a raw material supply pipe (center chute) 2 on the center axis of the upper part of the mill, and falls on a rotary table 3 which rotates at the lower part of the mill. Centrifugal force acts on the raw material to be pulverized on the rotary table 3, and the raw material is fed onto a pulverizing ring 18 on the outer periphery of the rotatable table 3. On the race 19, the powder is compressed and pulverized by the pulverizing roller 4. The pulverized particles produced by the pulverization are throat ring 25
Is transported above the mill while being dried by the hot air 17 blown into the mill. The fairly coarse particles fall on the rotary table 3 due to gravity and are again pulverized in the pulverizing section (primary classification). Particles penetrating this primary classifier are
It is centrifugally classified by the rotary classifier 22 (secondary classification). The relatively coarse particles are blown to the inner wall of the housing 14 by centrifugal force, fall by gravity, and are crushed again. The fine particles penetrate between the blades of the rotary classifier 22 and are discharged from the product fine powder discharge pipe 24 as product fine powder. For coal,
It is sent directly to a pulverized coal burner (hot air 17 becomes primary air for combustion) or collected in a storage bin.

FIG. 9 shows a crushing roller when a crushing roller 201 having a crushing curved surface extension 201b having the shortest circumferential length is combined with a roller bracket 205 having the smallest inclination angle (θ ₁ ). FIG. 2 schematically illustrates a pulverized state 201. FIG. In this figure, the compressed powder layer below the grinding roller is omitted. Since the tilt angle θ ₁ is small, the tilt angle θ ₁ easily moves outward like a pendulum, and the maximum swing angle φ ₁ is larger than φ of the other two grinding rollers. In addition, since the extension 201b of the grinding surface is short, the frequency of the resistance generated during the pendulum movement to the outside (mill housing side) is lower than that of the other grinding rollers, and the duration of the resistance is short. As described above, it can be said that the pulverizing section as shown in this figure has a structure in which the head is more easily swung outward than other pulverizing rollers.

FIG. 10 shows that the inclination angle is the largest (θ ₃ ).
The roller bracket 405 has an extended portion 401b of the crushed curved surface.
7 schematically illustrates a pulverized state when the longest pulverizing roller 401 is combined in the circumferential direction. In the crushing roller 401, the inclination angle is the largest (θ ₃ ).
Since the roller bracket 405 is used, the crushing roller is in a considerably inclined state from the beginning, and it is difficult to swing outward. Even if the head is shaken back to the inside, the raw material is supplied one after another, and as a result, the swinging motion is suppressed. Maximum swing angle phi ₃ is the smallest as the slope angle of the grinding rollers in the same mill. Further, since the circumferential direction of the extended portion 401b of the crushing curved surface is the longest, the crushing roller 401
Is the longest of the three grinding rollers per revolution of the grinding roller.

In the roller mill according to the present embodiment, since three crushing rollers are provided, the other crushing roller requires θ ₂ +
It is a combination of Lβ.

In any case, the synergistic effect of the difference in the contact state between the roller and the powder layer due to the different inclination angle of each roller and the difference in the cycle of compressing the powder layer by the crushing curved surface extension changed for each roller. The effect is that the movements of the rollers cancel each other out and prevent in-phase movements that amplify to the most intense self-excited vibration.

FIG. 11 summarizes changes in the amplitude of vibration with respect to coal hold-up in a mill, and compares the embodiment of the present invention with the conventional example. Vertical axis amplitude δ
_0C is dimensionless by dividing by the amplitude δ _0C ^* at the time of metal touch (idle rotation without any coal). On the other hand, the hold-up W on the horizontal axis is dimensionless by being divided by the hold-up W ^* when the mill is operated at the rated load. This experiment was conducted on coal which is liable to vibrate. In the prior art, the amplitude is remarkably large in a low load band (W / W ^* ≒ 0.3), whereas in the case of the roller mill using the crushing roller and the roller bracket according to the present invention, a significant reduction in vibration is achieved. It was confirmed that it was possible. In the roller mill according to the present invention as well, the amplitude increases when W / W ^* ≒ 0.3, which is considered to be a type of forced vibration. In the embodiment of the present invention, the amplitude at the time of metal touch is slightly larger than the conventional example. This is considered to be due to imbalance due to forced vibration caused by changing the inclination angle of the crushing roller for each crushing roller in the example of the present invention.

FIG. 12 is a test result in the case of using coal which is unlikely to cause vibration. Both axes are dimensionless in the same manner as in FIG. 11, and the relationship between the hold-up and the amplitude is summarized. Compared with the example of coal which is liable to cause vibration as shown in FIG. 11, the amplitude of the conventional technology is considerably small, but still the vibration of δ _0C / δ _0C ^* ≒ 2.4 occurs. On the other hand, it is understood that the use of the roller bracket and the crushing roller embodying the present invention can reduce the amplitude _δOC to a considerably low level.

FIG. 13 shows the change in the particle size of the product fine powder with respect to the amount of coal supplied. The particle size q on the vertical axis is divided by the reference particle size q ^* in the conventional mill at the rated coal supply Q. The horizontal axis is dimensionlessly displayed by dividing by the rated coal supply Q. Generally, the particle size q decreases in proportion to the coal supply amount Q. In the examples according to the present invention, it was found that the product fine particles had almost the same particle size as compared with the conventional roller mill. In other words, it can be seen that there is no significant difference in the pulverization performance when the structure of the pulverization unit is improved to the extent embodied in the present invention.

The amount of wear was compared for each grinding roller. The result is shown in FIG. Among the three crushing rollers, the roller bracket 205 having the smallest inclination angle (θ ₁ ) and the crushing roller having the shortest extension of the crushing curved surface (Lα) have the largest wear amount, and the maximum inclination angle θ ₃ + It is about 6% more than the wear of the combination of the longest grinding surface extensions Lγ. This is because θ ₁ + Lα, as shown in FIG.
Is considered to shake the head most vigorously as compared with the other grinding rollers. After a long period of use, the difference in the amount of wear for each crushing roller becomes remarkable, and if it seems that it is likely to have an adverse effect on vibration suppression, replace the crushing rollers used in the same mill. Good. That is,

[0034]

(Equation 3) The combination is changed as follows.

The roller mill according to the present invention is not limited to a mill for a pulverized coal-fired boiler, a mill for a solid fuel-fired boiler such as petroleum coke, and a mill for cement finishing or a pig steel slag. It can be applied almost directly to a pulverizing mill or a blast furnace blown pulverized coal mill. Especially in the field of cement recently, especially under strict quality control and energy saving operation,
The roller mill according to the invention is considered to be particularly effective.

[0036]

In the roller mill according to the present invention, the vibration of the mill caused by the sliding of the grinding roller can be greatly reduced. Therefore, the minimum load of the operable mill can be reduced, whereby the operating load range of a plant using the mill, for example, a coal-fired boiler, a thermal power plant using the boiler, and the like can be expanded.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a roller mill and an embodiment of the present invention.

FIG.

FIG. 3 and

FIG. 4 is a view showing a roller bracket of the roller mill according to the present invention.

FIG. 5 (A) and (b),

FIG.

FIG. 7 and

FIG. 8 is a view showing a pulverizing roller of a roller mill according to the present invention.

FIG. 9 and

FIG. 10 is a schematic view of a mechanism of a pulverizing roller of a roller mill according to the present invention.

FIG.

FIG.

FIG. 13 and

FIG. 14 is a diagram showing the results of various tests using the roller mill according to the present invention.

FIG.

FIG. 16 and

FIG. 17 is a view showing characteristics and mechanism of vibration in a conventional roller mill.

FIG. 18 is a configuration diagram of a pulverizing roller and a roller bracket in a conventional roller mill.

[Explanation of symbols]

1 ... raw material to be ground, 2 ... raw material supply pipe, 3 ... rotating table,
4 crushing roller, 5a crushing curved surface of crushing roller, 5b
Extension of grinding surface, 6: roller bracket, 7: roller shaft, 9: pivot box, 10: roller pivot, 11: pivot box, 12: spring, 13
... Spring frame, 14 ... Mill housing, 15 ...
Throat vane, 18: crush ring, 19: crush race, 21: compressed powder layer, 22: rotary classifier.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruaki Tatema 6-9 Takaracho, Kure-shi, Hiroshima Babcock Day Inside Kure Factory, Ltd. (72) Inventor Tadashi Hasegawa 6-9 Takaracho Kure-shi, Hiroshima Babcock Day (72) Inventor Yoshinori Taoka 6-9 Takara-cho, Kure-shi, Hiroshima Prefecture Babcock Hitachi Kure Factory (56) References JP-A-2-107347 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B02C 15/00-15/16

Claims (4)

(57) [Claims] 1. A rotary table that rotates in a horizontal plane below a mill housing, a grinding race provided on an outer peripheral portion of an upper surface of the rotary table, and a plurality of grinding rollers mounted on the race and rotated by being pressed. A roller bracket that rotatably supports each of the crushing rollers, and a roller pivot that supports each of the roller brackets so as to allow the pendulum to move, and at least one of a roller mill that crushes the raw material to be crushed by the crushing roller and the crushing race. A roller mill, wherein a mounting angle (θ) of a crushing roller with respect to a vertical line is configured to be different from the mounting angle of another crushing roller. 2. The roller mill according to claim 1, wherein each of the pulverizing rollers has a different mounting angle with respect to a vertical line. 3. The roller mill according to claim 1, wherein a difference between mounting angles of the crushing rollers is within 2 degrees. 4. A rotary table rotating in a horizontal plane below the mill housing, a grinding race provided on an outer peripheral portion of an upper surface of the rotary table, and a plurality of grinding rollers mounted on the race and rotated by being pressed. A roller bracket that rotatably supports each of the grinding rollers, and a roller pivot that rotatably supports the roller brackets. An extension of the grinding surface is provided on the outside in the vertical direction, and the radius of curvature and the center of curvature of this extension match the one of the grinding surface ,
Grinding the extension on at least one grinding roller
Roller circumference (rotation) direction length is set to other grinding rollers.
A roller mill having a length different from the above-mentioned length .