JPH05138052A - Roller mill - Google Patents

Abstract

PURPOSE:To provide a roller mill made adaptable to a wide range of load or many kinds of coals without generating large vibration by preventing that grinding rollers are synchronously oscillated or moved up and down. CONSTITUTION:In a roller mill equipped with a plurality of the grinding rollers 5 supported in a rotatable manner by the roller brackets 6 arranged on the upper surface of the outer periphery of a turntable 3 and the pressure frame 9 supporting the grinding rollers through roller pivots 8 and the roller brackets 6 in a state possible to oscillate to press them to the turntable 3, the pressure frame is constituted of independent frame members divided at every grinding rollers and the adjacent frame members are bonded by mechanical bonding means 22,23,24 different in the modulus of elasticity to be formed as one pressing force transmission member.

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 having an improved pressure frame structure in order to suppress a large vibration even under a low load and enable stable operation.

[0002]

2. Description of the Related Art In a coal-fired boiler, low pollution combustion (low N
Ox, reduction of unburned matter in ash) and wide-area load operation are being implemented, and accordingly, improvement in performance of pulverized coal machines (mills) is also required. As one type of mill for finely crushing lumps such as coal, cement raw materials, and new raw materials, vertical roller mills that perform crushing with a rotating table and multiple rollers have come into widespread use. We are solidifying our position as one of the representative models.

This type of mill has a substantially disk-shaped rotary table which is located at the bottom of a cylindrical housing and is driven by a motor to rotate at a low speed through a speed reducer. It is provided with a plurality of crushing rollers that are rotated by being pressed by a hydraulic pressure (or a spring or the like) to positions equally divided in the direction. The raw material to be crushed, which was supplied from the chute to the center of the table, moves to the outer periphery of the table in a spiral shape on the table by centrifugal force, and is caught between the crushing race surface of the table and the crushing rollers. Be crushed. Hot air is introduced through a duct to the lower part of the mill housing, and this hot air is blown up from a slit-shaped air throat between the outer circumference of the table and the housing. The crushed powder is dried while rising in the housing by the hot air blown up from the air throat. The granular material transported to the upper part of the housing falls from the coarse material due to gravity (primary classification) and is pulverized again in the pulverizing section. The fine powder particles passing through the primary classifying section are classified again by a cyclone separator or a rotary separator (rotary classifier) provided on the upper part of the housing. Fine powder having a particle size smaller than a predetermined particle size is conveyed by an air flow and is sent to a pulverized coal burner or a fine powder storage bin in a boiler. The coarse powder having a predetermined particle size or more, which has not passed through the classifier, is dropped onto the table by power and is pulverized again together with the raw material just supplied to the mill. In this way, pulverization is repeated in the mill to produce fine product powder.

[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. Although this vibration phenomenon is complicated and the detailed mechanism is not clarified, it is a kind of frictional vibration (stick / slip motion known as a representative of discontinuous / non-linear vibration) caused by the slip between the coal bed and the roller. Is considered to be. As the type of vibration, because the excitation source cannot be clearly specified,
It can also be said to be a type of self-excited vibration because the vibration waveform has a spike shape. With normal coal, as shown in Fig. 7, during low-load operation (coal holding amount in the mill (hold-up)
This condition becomes more severe under the condition that the load is small, but it may occur at a considerably high load depending on the coal type.

FIG. 11 is a sectional view showing a supporting structure of a conventional grinding roller. In this type of roller mill, the crushing roller 1101 is swingably supported via the roller bracket 1106 with the roller pivot 1108 as a spindle. This swinging function is very important, and when the crushing roller 1101 bites in a foreign substance such as an iron piece that is difficult to be crushed, the crushing roller 1101 can avoid an impact by shaking its head. Further, when the grinding roller 1101 and the grinding race 1117 are worn, this swinging mechanism also has the function of automatically finding an appropriate pressing position (positional relationship between the grinding roller 1101 and the grinding race 1117). As shown in FIG.
3 grinding rollers (or roller bracket 1106)
Are held under each side of the equilateral triangular pressure frame 1109.

Generally, at the time of high load crushing, the crushing roller 11
01 has little shaking and rotates extremely stably. As described above, when the crushing roller 1101 vigorously bites the raw material at the time of starting the mill, increasing the load, etc., the crushing roller 1101 shakes its head. Does not sync. At this time, the mill starts to vibrate, but the dominant frequency cannot be specified because the movements of the crushing roller 1101 are not synchronized, and the frequency distribution is broad, so-called forced vibration.
It will not interfere with the operation of the mill.

On the other hand, when the rollers vigorously vibrate by self-excitation, as shown in FIG. 8, all three grinding rollers 801 laterally shift outward (β), and then vibrate vertically as shown in FIG. .. The three crushing rollers vertically vibrate together (in phase) together. As shown in FIG. 10, when one of the crushing rollers causes a lateral displacement-like swinging motion (β) and vertical vibration (γ) of the crushing roller occurs, this motion is caused by the integral pressing frame 1109 or the table or powder bed. And propagates to other crushing rollers. This is the cause of the in-phase vibration of the grinding roller.

From the above, in order to suppress the vibration of the mill by devising the hardware of the crushing section, it is essential that the three crushing rollers move synchronously, that is, prevent the same phase movement. I understand. The object of the present invention is, based on the above idea, to prevent the crushing roller from oscillating in a synchronized manner, or to prevent a vertical vibration, and to operate in a wide area load or in a multi-carbon type without causing a large vibration. It is to provide a roller mill that enables it.

[0009]

In order to achieve the above object, the first invention of the present application is to provide a rotary table which rotates about a vertical axis on a horizontal plane in a housing, and a roller bracket which is arranged on an outer peripheral upper surface of the rotary table. In a roller mill provided with a plurality of rotatably supported crushing rollers and a pressure frame for oscillatingly supporting the crushing rollers via a roller pivot and a roller bracket and pressing the rotary table, each crushing roller An independent frame body member is provided, and the adjacent frame body members are joined by mechanical joining means having different backlash and / or frictional force to constitute the pressurizing frame as one pressing force transmitting member. Regarding roller mill.

According to a second aspect of the invention, a rotary table which rotates about a vertical axis on a horizontal plane in the housing, a plurality of crushing rollers arranged on the outer peripheral upper surface of the rotary table and rotatably supported by roller brackets, and rollers. In a roller mill having a pivot and a pressure frame that supports a crushing roller via a roller bracket so that the crushing roller can be swung, and the pressure frame is provided with an independent frame member for each crushing roller. The present invention relates to a roller mill in which the frame members of adjacent rollers are joined together by mechanical joining means having different elastic coefficients to form an integrated pressing force transmission member.

[0011]

Operation One of the three crushing rollers momentarily slides laterally as shown in FIG. 8 due to the internal collapse of the powder layer under the roller, and further vertically vibrates (sticks) as shown in FIG.・ Slipping motion), if the pressure frame is composed of the same member, this movement immediately propagates to the other grinding rollers, and the three grinding rollers are synchronized (in phase). The mill is prone to severe self-excited vibration. On the other hand, when the pressure frame is connected by a mechanical joining means to form a frame body as in the present invention, friction between metal surfaces of the connecting portion or a slight gap (backlash) between the metal surfaces is caused. , The generated vibration is attenuated. In particular, if the change in the gap is restrained by a member whose elastic constant is changed for each pressure frame for each roller, the damping effect is further improved. Therefore, even if one of the crushing rollers vibrates, the other crushing rollers do not follow it, and the self-excited vibration that occurs is eliminated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention lies in the structure of the pressing frame for transmitting the pressing force to the crushing roller. Therefore, this will be explained first and the structure of the entire mill will be described later. As shown in Figure 1,
In the roller mill to which the present invention is applied, the rotation support portion of the roller shaft 10 of the crushing roller 5 is installed on the roller bracket 6. A roller pivot 8 is inserted in the upper part of the roller bracket as a load transmission point to the crushing roller 5 and the roller bracket 6 and a rotation supporting portion for the swinging motion of the crushing roller 5. The pressing frame 9 presses the roller pivot 8 from above. A crushing load is applied to the pressurizing frame 9, which is caused by pulling the tension rod 25 downward by hydraulic pressure (downward pulling force 29).

FIG. 2 is a view of the pressure frame 9 as seen from above. . In the embodiment of the present invention, there are three crushing rollers 5 and the assembled pressure frame 9 has an equilateral triangle. For each crushing roller 5 and roller bracket 6, the pressure frame 9 is divided as a frame member 9a and is independent of each other. Each frame member 9a is connected at both ends thereof via a pressure frame connecting member 22 by a connecting elastic member 23 and an elastic member fixing tool 24 to form an equilateral triangle as the pressure frame 9. One end of the pressure frame connecting member 22 projects to the outside of the housing 17 and is joined to the tension rod 25. FIG. 3 is a sectional view showing the detailed structure of the connecting portion of the pressure frame 9. Basically, the frame member 9a of the pressure frame and the pressure frame connecting member 22 are connected by an elastic member fixing tool 24 which is a mechanical joining means combining bolts and nuts. However, the portion corresponding to the bolt and the pressure frame connecting member 22
A spring as the connecting elastic member 23 is inserted between the two. In this way, the pressure frame frame member 9a
The connecting portion of (1) retains the function of connecting and fixing by tightening the bolt / nut with the elastic force of these springs (similar to a spring washer but having a small elastic coefficient).

Since the entire structure of the pressure frame 9 is an equilateral triangle, there are three connecting portions of the above pressure frame frame member 9a in the mill. In the example of the present invention, the connecting elastic member 2 used at the three connecting portions.
The elastic constant ki of 3 (i = 1 to 3) is changed. That is, k ₁ ≠ k ₂ ≠ k ₃ is set at the _three connecting portions. Specifically, springs having three different lengths are used. On the other hand, there is also a method in which the elastic constants of the left and right (FIG. 3) connecting elastic members 23 are made different in the same connecting portion. That is, k ₁₁ ≠
With k ₁₂ , k ₂₁ ≠ k ₂₂ and k ₃₁ ≠ k _32, and at three connecting parts in the mill,

[0015]

[Equation 1]

As a method, the ratio of the elastic constants of the left and right springs is made different. In short, for the arrangement of the elastic constant k of the connecting elastic member 23 used in the same mill,
The "regularity" is eliminated as much as possible, that is, k is randomly configured. The connecting elastic member 23 is not always necessary. Pressure frame frame member 9
It is not necessary when a and the pressure frame connecting member 22 are firmly joined to each other to ensure sufficient reliability. in this case,
Although the elastic constant k cannot be changed significantly, if the backlash and friction between the pressure frame connecting member 23 and other members are different at each connecting portion, the in-phase motion of the crushing roller can be prevented. By doing so, as compared with the prior art in which the pressure frame is integrally molded as shown in FIG. 11, a large amount of backlash or frictional force is generated at each connecting portion of the pressure frame 9, and the exciting force generated at the crushing portion is generated. , The function of attenuating it works effectively. Further, the existence of this connecting portion is also effective for the propagation of vibration, that is, the division of the feedback loop of the self-excited system.

Although the order is reversed, the entire structure (FIG. 1) of the roller mill equipped with the pressing frame constituting the present invention will be described here. The raw material 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 rotating at the lower part of the mill. Centrifugal force acts on the material to be ground on the rotary table 3,
The powder is fed onto the crushing ring 12 on the outer periphery of the upper surface of the rotary table 3, and is crushed and crushed by the crushing roller 5 on the crushing race 13 having a substantially circular cross section carved on the upper surface of the crushing ring 12. It The pulverized powder and granules penetrate between the throat vanes 15 and are dried by the hot air 18 blown into the mill while being transported to the upper part of the mill. The coarse particles fall on the rotary table 3 due to gravity (primary classification), and are crushed again in the crushing section. The particle group penetrating the primary classification part is centrifugally classified by the rotary classifier 26 having a large number of rotary blades (secondary classification). The relatively coarse particles are blown to the inner wall of the housing 17 by centrifugal force, fall by gravity and are re-ground. The fine particles penetrate between the blades of the rotary classifier 26 and are discharged from the product fine powder discharge duct 28 as product fine powder. In the case of coal, it is sent directly to the pulverized coal burner (the hot air 18 becomes the primary air for combustion) or is collected in a storage bin.

When the pressure frame for a roller mill according to the present invention is used, the feedback loop of the self-excited vibration that is about to occur is divided by friction or backlash in the joint portion of the frame body, or the expansion and contraction action of the interposed spring. That is, even if the crushing roller shakes its head synchronously and self-excited vibration begins, the movement of the crushing roller is canceled by the joining portion of the pressing frame, and the vibration is eventually suppressed. Here, the self-excited vibration suppressing effect of the pressurizing frame in the present invention and the crushing characteristics related thereto will be described based on the test results.

FIG. 4 summarizes changes in vibration amplitude with respect to coal hold-up in the mill and compares the embodiment of the present invention with the prior art. Amplitude δoc on the vertical axis
Is the amplitude δoc during metal touch (idle rotation without coal)
It is divided by ^* to make it dimensionless. On the other hand, the holdup W on the horizontal axis is made dimensionless by dividing by the holdup W ^* when the mill is operated at the rated coal feed rate. The results of this experiment were obtained when crushing coal, which is susceptible to severe vibration. In the conventional technique, the amplitude is remarkably large in the low load region (W / W ^* to 0.38), but when the pressurizing frame of the present invention is applied, the amplitude can be significantly reduced. It was proven.
Also in the roller mill of the present invention, the amplitude becomes slightly larger at W / W ^* to 0.38, which is considered to be one type of forced vibration. In the embodiment of the present invention, the amplitude during idle rotation (metal touch) is slightly larger than that in the prior art. This is a random load fluctuation due to backlash and friction at the joint of the pressure frame of the roller mill according to the present invention,
In other words, it is considered to be due to forced vibrational imbalance operation. As described above, such "backlash" and "friction" have a function of suppressing or damping self-excited vibration. In other words, the present invention changes the type of vibration from "vigorous self-excited vibration" to "weak forced vibration" (backlash and friction cause forced vibration).

FIG. 5 shows the test results using coal whose self-excited vibration is generated but its degree is weak. In the same manner as in FIG. 4, both axes are made dimensionless and the relationship between holdup and amplitude is summarized. There is. Compared with the example of coal that is prone to violent self-excited vibration as shown in FIG. 4, although the amplitude is small in the conventional technique, it is still δoc / δoc ^* to 3.2.
Is vibrating. On the other hand, in the present invention, it can be seen that the amplitude δoc can be reduced to a considerably low level.

FIG. 6 shows the product fine particle size q with respect to the coal supply amount C.
It shows the change of. The particle size q on the vertical axis is divided by the standard fine powder particle size q ^* in the conventional mill at the rated coal feed amount C ^* and is expressed as a relative value. The horizontal axis is also divided by C ^* to make it dimensionless. Generally, the grain size q decreases as if it is inversely proportional to the coal supply amount C. 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 there is no great difference in the grinding performance of the roller mill.

The roller mill according to the present invention is not limited to the mill for coal-fired boilers described as a specific example, but a mill for oil coke, which is the same solid fuel, a mill for finely pulverizing desulfurized coal stone, It can be applied almost as it is to a mill for finely crushing steel slag and non-ferrous slag, a mill for cement finishing to finely crush cement clinker, and a mill for finely crushing raw materials of various chemical products.

[0023]

According to the present invention, accidents and noise due to self-excited vibration of the roller mill can be prevented. As a result, the reliability and durability of the mill itself and the plant-related equipment around the mill are improved. Further, since vibration can be suppressed in the low load zone, wide range load operation of not only the mill but also related equipment such as the entire boiler becomes possible. In addition, coal species and solid raw materials that have been feared to be susceptible to vibration can be used without any problems. This greatly expands the types of raw materials that can be milled.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a roller mill according to the present invention.

[Fig. 2]

FIG. 2 and FIG. 3 are structural views of a pressure frame in the roller mill of the present invention.

[Fig. 4]

[FIG. 5]

FIG. 4, FIG. 5, and FIG. 6 are explanatory diagrams of test results of the roller mill according to the present invention.

[FIG. 7]

FIG. 8

FIG. 9 and

FIG. 7, FIG. 8, FIG. 9 and FIG. 10 are explanatory views of problems in the conventional technique.

FIG. 11

FIG. 11 and FIG. 12 are structural views of a crushing unit of a conventional roller mill.

[Explanation of symbols]

3 ... rotary table, 5 ... grinding roller, 6 ... roller bracket, 7 ... pivot box, 8 ... roller pivot, 9
... Pressure frame, 12 ... Grinding ring, 14 ... Powder layer, 15
… Throat vanes, 17… Housing, 18… Hot air, 2
2 ... Pressure frame connecting member, 23 ... Connecting elastic member, 2
4 ... Elastic member fixing tool, 25 ... Tension rod, 26 ...
Rotary classifier.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi Co., Ltd. Kure Factory (72) Yoshinori Taoka 6-9 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi Ltd. Company Kure Factory (72) Inventor Tadashi Hasegawa 6-9 Takaracho, Kure City, Hiroshima Prefecture Babkotsk Hitachi Ltd. Kure Factory

Claims (2)

[Claims] 1. A rotary table which rotates about a vertical axis on a horizontal plane in a housing, a plurality of crushing rollers which are arranged on an upper surface of an outer periphery of the rotary table and rotatably supported by a roller bracket, a roller pivot and a roller bracket. In a roller mill equipped with a pressing frame that supports the crushing roller so that the crushing roller can be swung via a roller and a pressing frame that presses against the rotary table, an independent frame member is provided for each crushing roller, and there is play between adjacent frame members. Alternatively, a roller mill is characterized in that the pressure frame is configured as one pressing force transmission member by being joined by mechanical joining means having different frictional forces. 2. A rotary table which rotates about a vertical axis on a horizontal plane in a housing, a plurality of crushing rollers which are arranged on an outer peripheral upper surface of the rotary table and rotatably supported by a roller bracket, a roller pivot and a roller bracket. In a roller mill that includes a pressing frame that supports the crushing roller so that the crushing roller can be swung through the pressing table and a pressing frame that presses the rotating table, the pressing frame is provided with an independent frame member for each crushing roller, and each adjacent roller 2. The roller mill, wherein the frame members are joined together by mechanical joining means having different elastic coefficients to form an integrated pressing force transmitting member.