JPH05104009A - Roller mill - Google Patents

Abstract

PURPOSE:To prevent large vibrations due to the synchronization of the self- activated vibrations of each crushing roller in a roller mill equipped with more than one crushing rollers. CONSTITUTION:A roller mill is equipped with the following devices: a rotary table 3 revolving on the horizontal surface in the lower part of a housing 6; more than one crushing rollers 7 arranged on crushing races 6 on the upper surface of the table; roller brackets 8 which are installed on each crushing roller 7 and support the crushing rollers 7 to rotate; pressure frames 12 which support the roller brackets to enable to oscillate through roller pivots 10 and pressure the brackets downward. Each roller bracket is equipped with more than one roller pivots 10. The lines connecting these roller pivots 10 with the pressure transmission parts of the roller brackets 8 form inclined angles to the upper surface of the rotary table 3, and the inclined angles are arranged to be different for each of the roller brackets 8.

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 applicable to a wide area load operation in which a large vibration due to synchronization of self-excited vibration of each roller which occurs when a load is low is prevented.

[0002]

2. Description of the Related Art Even in a coal-fired boiler, low-pollution combustion (low NOx, reduction of unburned content) and wide-area load operation (change of coal supply amount) are carried out, and high-performance pulverized coal machine (mill) is accompanied with it.
Came to be requested. A vertical roller mill equipped with a crushing table and a plurality of crushing rollers is used as one type of crusher for finely crushing solid fuel typified by coal, cement raw materials such as limestone, and lumps of new raw materials. , Recently, it is solidifying its position as one of the representative models.

As can be seen from FIG. 4, this type of mill is
A disk-shaped rotary table 3 which rotates at a low speed on a horizontal plane driven by a motor having a speed reducer and which is located below a cylindrical housing (container) 26, and an outer peripheral portion of its upper surface is equally divided in the circumferential direction. It is provided with a plurality of crushing rollers 7 which are rotated by being pressed by a hydraulic pressure, a spring or the like to a position. The raw material to be pulverized, which is supplied from the raw material supply pipe 2 to the central portion of the rotary table, moves to the outer peripheral portion in a spiral trajectory on the table due to the rotation of the rotary table and the centrifugal force generated thereby, and the pulverizing race of the table is performed. It is crushed by being inserted between the surface of No. 6 and the crushing roller. The hot air 18 sent through the duct is guided to the lower part of the mill housing, and the hot air is blown through an air throat vane 19 between the outer peripheral part of the crushing table and the inner peripheral part of the mill housing. Up
The powder and granules produced by the pulverization are dried while rising in the mill housing by the hot air blown from the ace throat. The granular material transported to the upper part of the housing falls from the coarse one due to gravity (primary classification), and the slightly fine granular material penetrating there is re-used by the cyclone separator or the rotary classifier 15 provided on the upper part of the housing. Classified, fine powder having a predetermined particle size or less is conveyed by hot air, and is sent to a pulverized coal burner or a fine powder storage bin in a boiler. Coarse particles having a predetermined particle size or more that do not pass through the classifier fall on the crushing table and are crushed again together with the raw material just supplied to the mill. In this way, the crushing roller repeats the crushing.

[0004]

When the roller mill is to be operated at a low load, the vibration of the mill is a problem in reducing the load. This vibration phenomenon is complicated and its detailed mechanism has not been clarified. It is believed that there is. As the type of vibration, it is a kind of self-excited vibration because the excitation source cannot be clearly specified and the vibration waveform has a spike shape. As shown in FIG. 11, with normal coal, this vibration becomes severe during low load operation (conditions where there is little coal hold-up in the mill), but depending on the type of coal, it can occur even at considerably high load. is there.

14 and 15 show a supporting structure of a conventional crushing roller as a sectional view and a view from the mill housing side. In this type of roller mill, the roller pivot 120 is connected via the roller bracket 1202.
A crushing roller 1201 having a rotating roller shaft supported by a roller bracket is supported so as to be swingable around 07 as a spindle. This swinging function is very important, and when the crushing roller 1201 bites in a foreign substance such as an iron piece that is difficult to be crushed, the crushing roller 1201 can avoid a collision by shaking its head. Further, when the crushing roller 1201 and the crushing race 1212 are worn, an appropriate pressure position (crushing roller 1201 and crushing race 121
This swing function also has the effect of automatically finding the (positional relationship with 2).

Generally, at the time of high load crushing, the crushing roller 12
01 almost does not shake his head. As mentioned above,
When the crushing roller 1201 vigorously bites the raw material at the time of starting the mill or increasing the load, the crushing roller 1201 shakes its head.
The movements of the individual grinding rollers are not synchronized. At this time, the mill vibrates, but the dominant frequency cannot be specified because the crushing rollers 1201 are not synchronized, and the frequency distribution is broad forcible vibration, which does not hinder the operation of the mill.

On the other hand, when the rollers vigorously vibrate by self-excitation, as shown in FIG. 12, all three grinding rollers 1001 laterally shift outward (β), and then vibrate vertically as shown in FIG. .. At this time, the three crushing rollers vibrate vertically in synchronization (in phase). From the above, in order to suppress the vibration of the mill by devising the hardware of the crushing unit, when each crushing roller shakes its neck, a recovery force that tries to return to a normal orbit is generated and at the same time three It can be seen that it is essential that the crushing rollers of 1 move synchronously, that is, prevent the in-phase movement. Based on the above idea, the object of the present invention is to prevent the crushing roller from oscillating or vertically vibrating in synchronization, and it is possible to operate in a wide area load or a multi-carbon type without causing vibration. The present invention provides a roller mill device.

[0008]

To achieve the above object, the first invention of the present application is to provide a rotary table which rotates in a horizontal plane below the housing, a crushing race provided on the outer periphery of the upper surface of the rotary table, and a crushing race. A plurality of crushing rollers installed at predetermined intervals above the roller bracket, a roller bracket that rotatably supports the rotation shaft of the crushing roller, and a front and rear symmetrical position sandwiching the crushing roller rotation shaft above the roller bracket. A roller mill having two pivot boxes, a roller pivot provided in each pivot box, and a pressure frame joined to the roller bracket via the roller pivot and transmitting a downward pressure force, the pressure frame comprising: The axis connecting the joint between the roller bracket and the roller bracket is inclined with respect to the upper surface of the rotary table, and the inclination angle is low. About roller mill, characterized in differently by being configured for each bracket.

A second invention of the present application is the same as the first invention, wherein the difference between the inclination angles of the roller brackets is 2 to.
The present invention relates to a roller mill characterized by being set at 2.5 degrees.
A third invention of the present application is to provide a rotary table which rotates in a horizontal plane below the housing, a crushing race provided on the upper surface of the rotary table, and a plurality of crushing rollers arranged on the crushing race at predetermined intervals. In a roller mill including a roller bracket that rotatably supports the rotation shaft of the crushing roller and a pressure frame that presses the crushing roller onto the crushing race through the roller bracket, between the lower surface of the pressure frame and the upper surface of the roller bracket. A wedge-shaped tilting body is interposed between the tilting body and the roller, and the pressing force of the pressure frame is transmitted to the roller bracket through the tilting body. The present invention relates to a roller mill characterized by being inclined.

A fourth invention of the present application relates to a roller mill according to the third invention, wherein the wedge angle of the inclined body is different for each roller bracket.

[0011]

In the present invention, the crushing roller is inclined in the circumferential direction of the rotary table to generate a recovery force (from the state of swinging the head in a lateral displacement state to the normal orbit), and the above-mentioned roller is provided for each crushing roller. By combining the two functions of changing the tilt angle, the amplitude and cycle during swinging are changed randomly, and the magnitude of the restoring force to the normal trajectory is made different. By these synergistic effects, the swinging motion that triggers the vibration of the roller is quickly returned to the normal state, and even if the head is shaken, the motion is made random for each roller, resulting in self-excited vibration. To prevent.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention lies in the supporting structure of the crushing roller, which will be described first. 1 to 3 show an inclined support structure of each crushing roller in the same roller mill. Referring to FIG. 1 as an example, first, a pressure frame 12 to which a crushing load is applied from above (this pressure frame 12 has a substantially equilateral triangular structure when viewed from above, and is formed at the bottom of the frame on each side of the triangle). A rectangular groove is formed on the lower surface of the roller (which supports the roller), and a substantially wedge-shaped inclined body 11 having an inclination angle θ ₁ is inserted therein. Two pivot boxes 9 are provided on the lower surface of the inclined body 11, and a roller pivot 10 for supporting the roller bracket 8 as if swingable is mounted. The roller rotating shaft 23 of the crushing roller 7 is fixed to the roller bracket 8 so as to be rotatable.
Both roller pivots 10 are arranged symmetrically with the roller rotation shaft 23 in between.

[0013] The support structure of the grinding roller shown in FIG. 2 is basically identical to that shown in FIG. 1, the inclination angle theta ₂
Is slightly smaller (θ ₂ <θ ₁ ). The distance L between the lower surface of the pressure frame 12 and the crushing race 6 is the same for all rollers in the same mill. This is done by the pressure frame 12
This is to keep the crushing race 6 and the crushing race 6 parallel to each other. In the crushing roller shown in FIG. 3, the inclination angle θ ₃ is set larger than the other two rollers (θ ₂ <θ ₁ <θ ₃ ). Although shown slightly exaggerated in the figure, the magnitudes of θ ₁ , θ ₂ and θ ₃ are θ ₂ = 2 °, θ ₁ = 4 ° and θ ₃ = 6.5 °.
Therefore, even such a size and deviation are sufficiently effective in suppressing vibration. If the tilt angle θ is too large,
_If the angle between _{1 and} θ ₃ is too different, the intervals between the crushing rollers (circumferential direction of the crushing ring) will be uneven or the rotation of the crushing rollers will be unstable due to the structure of the crushing section. There is a risk.

The inclined body is inserted and used to incline the roller bracket when the balance of the inclination of each roller is lost due to the abrasion of the roller and the crushing race (for example, the lower surface of the pressure frame 12 and This is because, when the distance L between the crushing races 6 is different for each roller), the balance of the pressure frame can be maintained by using the inclined body whose thickness is readjusted. Also, if the coal type has changed from the original plan, with the initial settings of θ ₁ to θ ₃ ,
There may be cases where it is inappropriate. Even in this case, it is possible to deal with the problem by changing the inclined body, which has a low manufacturing cost.

Although the order is reversed, the overall structure of the roller mill (FIG. 4) equipped with the roller bracket supporting device according to the present invention will now be described. A raw material 1 is supplied from a raw material supply pipe (center chute) 2 located on the central axis of the upper part of the mill and drops onto a rotary table 3 which rotates at the lower part of the mill. Centrifugal force acts on the raw material on the rotary table, and the raw material is fed to the crushing ring 4 on the outer periphery of the rotary table 3, and on the crushing race 6 whose cross section is engraved on the upper surface of the crushing ring 4 and has a substantially arc shape. The powder is crushed by the crushing roller 7.
The crushed powder particles are transported to the upper part of the mill while being dried by the hot air 18 blown into the mill through the throat vanes 19. Coarse particles have an upper limit of aerodynamic transport and fall onto the rotary table 3 due to gravity (primary classification) and are pulverized again in the pulverization section. The particle group penetrating the primary classifying portion is centrifugally classified by the rotary classifier 15 (secondary classification). The relatively coarse particles are blown to the inner wall of the housing 26 by centrifugal force, and are dropped by gravity and re-ground. The fine particles pass between the blades of the rotary classifier 15 and are discharged from the product fine powder discharge duct 17 as product fine powder. In the case of coal, it is directly sent to the pulverized coal burner (the hot air 18 becomes the primary air for combustion) or is collected in the storage bin.

When the raw material powder layer between the crushing roller and the crushing race is internally collapsed and the crushing roller slides laterally as shown in FIG. 12, when the supporting structure of the roller bracket according to the present invention is adopted, FIG. As shown in a view from above, the amounts of lateral deviation (amplitude of the swinging motion) between points A and B at both ends of the crushing roller 7 (when viewed from above) are different, that is, A
The lateral shift amounts L _A and L _{B of} → A ′ and B → B ′ are different, and the central axis 504 of the cross section of the crushing roller 7 is instantaneously inclined. As shown in FIG. 1, this is before and after the crushing roller (on the side of biting) and on the side (on the side of generating fine powder) of the oscillating radii R _B and R _A around the roller pivot 10 (FIG. 1). Because they are different. As described above, L _A ≠
When it becomes L _B , a restoring force (expressed as F in FIG. 5) that causes the crushing roller to return to the original normal rotation position is generated. FIG. 6 shows an example of no countermeasure that does not employ the inclined structure, but the crushing roller 7 causes lateral deviation in a substantially parallel manner from (a) to (b). In the present invention, since the inclination angle is changed for each crushing roller, this restoring force is different. This situation is shown in FIG. 7 as a view from above. When the tilt angle θ is made small (for example, FIG. 2), the restoring force F is small as shown in FIG. On the other hand, when the tilt angle is increased (the example of FIG. 3 corresponds to this), a large restoring force F is generated as shown in FIG. 7B.

As described above, in the present invention, even when the crushing roller is shaken with its head so as to be laterally displaced, the crushing roller has different restoration states in which the crushing roller tries to return to the normal orbit. Therefore, each crushing roller causes a swinging motion at random, and the amplitude and cycle of the swinging motion change for each crushing roller. In this way
Since the crushing rollers in the same mill cancel each other's swinging movements, it is possible to prevent the vigorous self-excited vibration in which the crushing rollers swing their heads in the same phase (synchronously) and vibrate up and down. Even if it occurs, it will be a weak forced vibration. Rather, it is the function of the roller bracket support device according to the present invention that, even if a certain crushing roller causes self-excited vibration, it is instantly damped, rather than preventing severe self-excited vibration.

FIG. 8 shows the coal hold-up in the mill.
Example of the present invention
And the prior art. Amplitude δ on the vertical axis_0CIs
Amplitude δ at metal touch (idle rotation without any coal)_0C ^*
It is divided by and made dimensionless. On the other hand, the horizontal axis hold
Up W is the ho when the mill is operated at the rated coal feed rate.
Led up W^*It is divided by and made dimensionless. This fruit
The test results were obtained when crushing coal, which is susceptible to vibration.
It was the one. In the conventional technology, low load (W / W ^* ~
0.37), the amplitude is remarkably large.
Vibration can be reduced significantly when a roller device is used.
Was confirmed. Grinding roller structure according to the present invention
W / W even for roller mills that use ^* ~Amplitude at 0.37
Is slightly larger, but this is one type of forced vibration
it is conceivable that. In the embodiment of the present invention,
The amplitude of the mushroom is slightly larger than that of the prior art. this is,
Swinging motion in the support portion structure of the crushing roller according to the present invention
It is caused by intentionally changing the amplitude and cycle of the work
Due to random load fluctuation, it is, so to speak, forced vibration and weak
It is thought to be due to unbalanced vibration.

FIG. 9 shows the results of a test using coal which is less likely to cause vibrations. As with FIG. 8, both axes are made dimensionless and the relationship between holdup and amplitude is summarized. Compared with the example of coal that is prone to violent vibration as shown in FIG. 8, the amplitude of the conventional technique is considerably small, but the vibration of δ _0C / δ _0C ^* to 2.9 is still generated. On the other hand, if the roller device embodying the present invention is adopted, it can be seen that the amplitude δ _0C can be reduced to a considerably low level.

FIG. 10 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 made dimensionless by dividing by the standard fine powder particle size q ^* in the conventional mill at the rated coal feed rate C ^* . Generally, the grain size q is the amount of coal supply C
Decreases as if inversely proportional to. In the examples according to the present invention, it was found that the particle size of the product fine powder is almost the same as that of the conventional roller mill. In other words, it can be seen that the crushing performance does not differ greatly even if the structure of the crushing roller supporting portion is improved to the extent that the present invention is embodied.

The roller mill according to the present invention is not limited to the mill for coal-fired boiler described as a specific example, but a mill for oil coke which is the same solid fuel, a mill for finely pulverizing limestone for desulfurization, and a cement. It can be applied almost as it is to mills for finely grinding steel slag and non-ferrous refining slag, which are raw materials for refractories, mills for cement finishing, which finely mills cement clinker, and mills, which finely mills raw materials for various chemical products. it can.

[0022]

With the roller mill embodying the present invention, vibration of the mill caused by slippage of the roller can be prevented. This improves the durability of various devices including the mill itself.
In addition, the reliability of the entire thermal power plant is increased. In addition, low load operation is possible, and the low load limit of the mill can be further reduced. As a result, the operating range of the coal-fired boiler will be expanded to the level of oil-fired. Since it is possible to burn coal exclusively in the low-load operation region, it is possible to reduce the consumption of the oil-based fuel for switching to the low load. Therefore, the entire coal-fired power plant can be operated more economically.

[Brief description of drawings]

1]

[Fig. 2]

FIG. 1, FIG. 2 and FIG. 3 are views showing a structure of a roller bracket of a roller mill according to the present invention.

FIG. 4 is an overall configuration diagram of a roller mill according to the present invention.

[FIG. 5]

FIG.

FIG. 5, FIG. 6 and FIG. 7 are diagrams schematically showing the mechanism of the roller mill of the present invention or the conventional roller mill.

FIG. 8

FIG. 9

FIG. 8, FIG. 9 and FIG. 10 are diagrams showing the test results of the roller mill of the present invention and demonstrating the effect thereof.

FIG. 11

FIG. 12

FIG. 11, FIG. 12 and FIG. 13 are views for explaining the problems of the conventional roller mill.

FIG. 14

FIG. 14 and FIG. 15 are views showing a structure of a roller bracket of a roller mill according to a conventional technique.

[Explanation of symbols]

1 ... Raw material, 2 ... Raw material supply pipe, 3 ... Rotating table, 4 ... Grinding ring, 6 ... Grinding race, 7 ... Grinding roller, 8 ... Roller bracket, 9 ... Pivot box, 10 ... Roller pivot, 11 ... Inclined body, 12 ... Pressure frame, 13 ... Pressure spring, 14 ... Spring frame, 15 ... Rotation classification, 17 ... Product fine powder discharge duct, 18 ... Hot air, 19
... throat vane, 22 ... compressed powder layer, 26 ... housing.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Eiji Murakami Eiji Murakami 3-36 Takaracho, Kure-shi, Hiroshima Babkotuku Hitachi Co., Ltd. Kure Research Institute (72) Eiichi Nishida 3-36 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi Stock Company Kure Institute (72) Inventor Hiroaki Kanemoto 6-9 Takara-cho, Kure-shi, Hiroshima Babkotuku Hitachi Co., Ltd. Kure Factory (72) Inventor Tadashi Hasegawa 6-9 Takara-cho, Kure-shi, Hiroshima Babkotuku Hitachi Kure Factory Within

Claims (4)

[Claims] 1. A rotary table which rotates in a horizontal plane below the housing, a crushing race provided on the outer periphery of the upper surface of the rotary table, a plurality of crushing rollers installed at predetermined intervals on the crushing race, and a crushing roller. A roller bracket that rotatably supports the rotating shaft of the two, two pivot boxes respectively provided in front and rear symmetrical positions sandwiching the crushing roller rotating shaft on the upper part of the roller bracket, and a roller pivot provided in each pivot box, In a roller mill provided with a pressure frame that is joined to a roller bracket via a roller pivot and transmits a downward pressure, an axis connecting the joining portion of the pressure frame and the roller bracket with respect to the upper surface of the rotary table. It is characterized in that it is inclined and the inclination angle is different for each roller bracket. Roller mill. 2. The roller mill according to claim 1, wherein the difference between the inclination angles of the roller brackets is 2 to 2.5 degrees. 3. A rotary table which rotates in a horizontal plane below the housing, a crushing race provided on the upper surface of the rotary table, a plurality of crushing rollers arranged at a predetermined interval on the crushing race, and a crushing roller. In a roller mill provided with a roller bracket that rotatably supports the rotating shaft of and a pressing frame that presses the crushing roller onto the crushing race through the roller bracket, a wedge-shaped roller is provided between the lower surface of the pressing frame and the upper surface of the roller bracket. The inclined body is interposed so that the pressing force of the pressing frame is transmitted to the roller bracket through the inclined body, and the line connecting the inclined body and the pressing force transmitting portion of the roller bracket is inclined with respect to the upper surface of the rotary table. Roller mill characterized by 4. A roller mill according to claim 3, wherein the wedge angle of the inclined body is different for each roller bracket.