JPH08155317A - Roller mill - Google Patents

Abstract

PURPOSE: To prevent self-exciting vibration of a roller mill by constituting at least one of a pulverizing roller and a pulverizing ring of plural segments, and differentiating pressing contact lines from each other every segment. CONSTITUTION: Pulverizing rollers 4 are rolled on a compressed powder bed on a pulverizing race 17 of a pulverizing ring 5. In this case, the pulverizing roller 4 is constituted of plural segments 21a, and in any segment 21a, a pressing contact line 20a is inclined against a conventional pressing contact line. And the inclined angles of pressing contact lines 20a are differentiated from each other every roller segment 21a. A pressing contact start point and a pressing contact finish point shown as both the ends of the pressing contact line 20a do not coincide with each other. Therefore, by mutual cancel action of plural pulverizing rollers, the generation of severe self-exciting vibration in which a roller mill is synchronously moved is damped to restrain it to a level of faint forced vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller mill for pulverizing coal, limestone, cement clinker and the like into fine powder.

[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 in coal supply amount) are carried out, and a high-performance pulverized coal machine (mill) is required accordingly. Came to be.

As one type of pulverized coal machine for finely crushing solid fuel typified by coal, cement raw material such as limestone or new raw material, a vertical type equipped with a crushing ring and a plurality of crushing rollers. Roller mill is used,
Recently, it is solidifying its position as one of the representative models.

The outline of a roller mill according to the prior art will be described below with reference to FIG.

A roller mill 1 of this type is a rotary table 3 on a circular plate, which is located at the bottom of a cylindrical housing (container) 2 and is rotated at a low speed on a horizontal plane driven by a motor having a speed reducer (not shown). And a plurality of crushing rollers 4 which are rotated by being pressurized with a hydraulic pressure or a spring to the position where the outer peripheral portion of the upper surface is equally divided in the circumferential direction, and are crushed by the rotary table 3, the crushing roller 4 and the crushing ring 5. Parts are made up.

On the other hand, coal is supplied from the raw material supply pipe 6 to almost the center of the rotary table 3, and the rotary table 3 is moved to the outer peripheral portion in a spiral shape by the rotation of the rotary table 3 and the centrifugal force generated thereby. It is crushed by being inserted between the crushing ring 5 and the crushing roller 4 of the rotary table 3.

On the other hand, under the housing 2, the hot air 7 sent through a duct (not shown) is introduced,
The hot air 7 is blown up from the throat vane 8 between the outer peripheral portion of the rotary table 3 and the inner peripheral portion of the housing 2.

The coal crushed in the crushing section of the roller mill 1 is dried while rising in the housing 2 by the hot air 7 blown up from the throat vane 8. The pulverized coal transported to the upper part of the housing 2 falls from the coarse one onto the rotary table 3 due to gravity (first classification), and the slightly fine pulverized coal passing therethrough is a cyclone provided on the upper part of the housing 2. The separator or the rotary classifier 9 classifies again, and the pulverized coal having a predetermined particle size or less is conveyed by the hot air 7 and sent to a pulverized coal burner or a pulverized coal storage bin of a boiler (not shown). Coarse pulverized coal having a predetermined particle size or more that does not pass through the rotary classifier 9 falls on the rotary table 3 and is pulverized again on the rotary table 3 together with the coal just supplied into the roller mill 1. In this way, the crushing roller 4 and the crushing ring 5 repeat the crushing.

In FIG. 16, 10 is a spring frame, 11 is a pressure spring, 12 is a pressure frame, 13 is a pivot box, 14 is a roller pivot,
Reference numeral 15 is a roller bracket, and 16 is a powder layer.

The supporting structure of the crushing roller will be described below with reference to FIG.

In the roller mill 1, the roller bracket 15
The crushing roller 4 is swingably supported via the roller pivot 14 as a support point. With this swinging function, when the crushing roller 4 bites a foreign substance such as an iron piece that is difficult to crush, the crushing roller 4 can avoid an impact by shaking the head. Further, when the crushing roller 4 and the crushing ring 5 are worn, this swinging function also has an action of automatically finding an appropriate pressing position (positional relationship between the crushing roller 4 and the crushing ring 5).

Generally, during high load crushing, the crushing roller 4 hardly shakes its head. However, when the crushing roller 4 actively bites the raw material when the roller mill 1 is started or when the load increases, the crushing roller 4 shakes its head, but in this swinging motion, the movements of all the crushing rollers 4 are synchronized. do not do. At this time, the roller mill 1 starts to vibrate, but because the crushing roller 4 is not synchronized, the dominant frequency cannot be specified, and the frequency distribution is broad, so-called forced vibration, and does not hinder the operation of the roller mill 1.

[0013]

When the roller mill 1 is to be operated under a low load, the vibration of the roller mill 1 becomes a problem in reducing the load. Although this vibration phenomenon is complicated and its detailed mechanism has not been clarified, it is considered to be a kind of frictional vibration caused by the slip of the coal powder layer 16 and the crushing roller 4. As the type of vibration, because the excitation source cannot be clearly specified,
Moreover, since the vibration waveform sharply sharpens like a spike, it can be said to be a type of self-excited abnormal vibration.

FIG. 19 shows the dimensionless amplitude (amplitude δ) on the vertical axis.
oc / amplitude δoc * during idling), and the characteristic that shows the coal hold-up in the roller mill (coal hold-up W in the roller mill / coal hold-up W * in the roller mill at the rated coal feeding load) that is dimensionless on the horizontal axis. It is a curve figure.

As shown in FIG. 19, during low-load operation (conditions in which coal hold-up in the roller mill is small), this vibration becomes severe as indicated by the diagonal lines, but depending on the type of coal, it may occur during considerably high-load operation. Even if there is, it may occur.

The manner in which the crushing roller vibrates violently under self-excitation will be described below with reference to FIGS. 17 and 18.

When the crushing roller vibrates vigorously by self-excitation, as shown in FIG. 17, the crushing rollers 4 are laterally displaced to the outside of the crushing ring 5 almost at the same time as shown by an arrow β.
Then, it vibrates up and down as shown by an arrow γ in FIG. All the grinding rollers 4 vibrate up and down together synchronously (in phase). When one of the crushing rollers 4 causes a laterally-displaced swinging motion (arrow β in FIG. 17) and vertical vibration of the crushing roller 4 (arrow γ in FIG. 18) occurs, this movement occurs in FIG.
Integrated pressure frame 12 or rotary table 3 shown in
And the powder layer 16 thereabove and propagate to the other crushing rollers 4. This causes the in-phase vibration of the crushing roller 4, and is not preferable for the roller mill 1.

The present invention is intended to eliminate the drawbacks of the prior art, and its object is to prevent self-excited vibration of the roller mill.

[0019]

In order to achieve the above-mentioned object, the present invention comprises at least one of a crushing roller and a crushing ring composed of a plurality of segments, and the pressing contact line is different for each segment. Is.

[0020]

If the shape of the crushing ring in the ring segment attached to the rotary table and the shape of the crushing surface in the segment of the crushing roller are different for each segment, the locus of the contact point between the crushing roller and the crushing ring becomes non-circular. Moreover, if the shape of the crushing ring or the shape of the crushing surface of the crushing roller is irregular with respect to the rotation direction, the non-circular locus drawn by each crushing roller on the crushing ring also differs for each crushing roller. . In this way, the pendulum movements of the grinding rollers are also completely out of sync with each grinding roller. The behavior of the crushing roller as described above except for the high load region condition (the powder layer is thick under this condition) in which self-excited vibration is extremely unlikely to occur even when there is a powder layer between the crushing roller and the crushing ring. , Basically the same.

Of the three crushing rollers, even if one crushing roller makes a large pendulum motion and causes side slip as shown in FIG. 17 and self-excited vibration is about to occur, the other crushing rollers move in this way. Does not follow The movements of the other two crushing rollers act so as to return the operation of the crushing roller, which causes self-excited vibration, to stable rotation because the shapes of the crushing surfaces of the crushing roller and the crushing ring are different. Due to the mutual canceling action of the plurality of pulverizing rollers, the occurrence of intense self-excited vibration in which the three pulverizing rollers move in phase, that is, in synchronization, is almost completely dampened and suppressed to the level of weak forced vibration. Will be.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a roller mill according to an embodiment of the present invention, FIG. 2 is a sectional view showing a crushing portion of FIG. 1, and FIG.
4 is an enlarged side view of the crushing roller, FIGS. 4 to 5 are development views showing the segments of the crushing roller, FIG. 6 is an enlarged sectional view of the connection between the segments of the crushing roller, and FIGS. 7 and 9 to 11 are the segments of the crushing ring. FIG. 8 is a cross-sectional view of the crushing ring, FIGS. 12 and 13 are diagrams for explaining the movement of the crushing roller, and FIG. 14 is a dimensionless amplitude (amplitude δoc) on the vertical axis.
/ Amplitude δoc * during idle rotation is shown, and the horizontal axis shows the non-dimensionalized coal hold-up amount in the roller mill (coal hold-up amount W in the roller mill / coal hold-up amount W * in the roller mill due to the rated coal feeding load) Fig. 15 is a particle size characteristic curve diagram in which the vertical axis represents the fine powder particle size and the horizontal axis represents the dimensionless coal supply amount.

1 to 13, reference numerals 1 to 16
Indicates the same as that of the prior art.

Reference numeral 17 is a crush race of the crush ring 5, 18 is a compressed powder layer, 19 is a central axis of the cross section, 20a and 20b are pressing contact points, 21a and 21b are segments, 22 is a shaft,
Reference numeral 23 is a notch groove.

In such a structure, the roller mill 1 according to the embodiment of the present invention has a crushing roller 4 and a crushing ring 5.
Is composed of a plurality of segments 21a and 21b. Before describing the segments 21a and 21b, an outline of the pressing contact lines 20a and 20b will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the crushing roller 4 is
On the crushing race 17 of the crushing ring 5, the compressed powder layer 18
Roll over. In this case, the crushing roller 4 shown in FIG.
The point a on the central axis 19 of the cross section and the point b on the crush race 17 are the pressing contact lines 20a and 20b. The pressing contact line 20a corresponds to the maximum point on the crushing curve of the crushing roller 4. That is, this pressing contact line 20a becomes a ridge line in the circumferential direction of the crushing roller 4.

On the other hand, the pressing contact line 20b of the crushing race 17
When flattening the tilted grinding race 17 (Fig. 2
In the figure, it indicates that the α-α line is converted horizontally), and the deepest position (bottom line) is shown.

The crushing roller 4 will be described below with reference to FIGS.
The pressing contact line 20a and the segment 21a will be described.

FIG. 3 is a side view of the crushing roller 4, which is composed of a plurality of segments 21a.

Reference numeral 22 in FIG. 3 is a shaft of the crushing roller 4.

FIG. 4 is a development view of the crushing roller 4 shown in FIG.

In this embodiment, the crushing roller 4 is composed of a plurality of segments 21a, and in any of the segments 21a, the pressing contact line (crushing ridgeline) 20.
a is inclined by an angle θ with respect to the pressure contact line A (dotted line in FIG. 4) of the prior art. Moreover, the inclination angle θ of the pressing contact line 20a differs for each roller segment 21a. Moreover, in FIG.
The pressure contact start point a and the pressure contact end point b shown as both ends (points a and b) of a do not match (the expressions "start" and "end" are defined based on the rotation direction). .

FIG. 5 shows the segment 21 of the grinding roller 4.
The other Example of the pressing contact line 20a in a is shown. In each segment 21a, the pressing contact line (crushing ridgeline) 20
a is moving substantially parallel to the pressing contact line (crushing ridgeline) A of the prior art shown by the one-dot chain line in FIG.

Further, the magnitude of this parallel movement is random with respect to the roller segment 21a, and the pressing contact point a and the pressing contact point b of the adjacent segments 21a are the same.
The roller segments 21a are arranged so as not to coincide with each other.

FIG. 6 is a sectional view of the connecting portion of the roller segment 21a. Even if the roller segments 21a having different shapes of the pressing contact line (crushing ridgeline) 20a are connected to each other, a cutout groove 23 is formed at the end thereof so as not to give an impact to the rolling of the crushing roller 4.

The pressing contact line 20b and the segment 21b of the crushing ring 5 will be described below with reference to FIGS. The crushing ring 5 is composed of a plurality of segments 21b.

FIG. 7 is a plan view showing the arrangement of the ring segments 21b, and is a view of the crushing ring 5 seen from above.
In contrast to the conventional arcuate pressure contact line (bottom line) B shown by the broken line in FIG. 7, the ring segment 21 of this embodiment is used.
In the arrangement of b, the pressing contact line (bottom line) 20b is obviously deviated from the arc of the pressing contact line B of the prior art. In this embodiment, the pressing contact line (bottom line) 20b is moved to the inside or the outside of the pressing contact line B of the prior art alternately every ¼ cycle of the crushing ring 5, that is, every 90 degrees. The segment 21b is arranged. Further, in the adjacent ring segments 21b, the pressing contact line 20b is smoothly connected.

8 (a) and 8 (b) are sectional views of the ring segment 21b.

In FIG. 8, the broken line shows the grinding race 17 of the conventional grinding ring 5, and the solid line shows the grinding race 17 of the grinding ring 5 according to the embodiment.

That is, the crushing race 17 of the prior art has a single arc, whereas the crushing race 17 according to the embodiment has the crushing race surface formed by smoothly connecting arcs having different curvature deformations.

In FIG. 8A, the crushing race 17 is formed so that the pressing contact line 20b is located outside the pressing contact line B of the prior art (on the side of the mill housing 2).

On the other hand, in FIG. 8 (b), contrary to FIG. 8 (a), the crushing race 1 is arranged so that the pressing contact line 20b is located inside the pressing contact line B of the prior art (center side of the rotary table 3).
7 are formed.

FIG. 9 shows another embodiment for the arrangement of the ring segments 21b. Similar to the embodiment of FIG. 7, the pressing contact line (bottom line) 20b shown by the solid line is
Prior art arcuate pressure contact line (bottom line) shown in broken lines
Although deviated from B, roughly speaking, the pressing contact line 20b has a rectangular shape. Compared with the embodiment of FIG. 7, the frequency with which the pressing contact line 20b moves in and out of the pressing contact line B of the prior art is doubled. By doing so, the frequency of minute pendulum movements of the crushing roller 4 also increases. Also in this embodiment, the pressing contact line (bottom line) 20b at all ends of each ring segment 21b.
The ring segments 21b are arranged so that they are connected smoothly.

FIG. 10 shows an embodiment in which the ratio of discontinuity of the tangent of the pressing contact line (bottom line) 20b at the end of the ring segment 21b is increased. Moreover, the pressing contact line (bottom line) in all the ring segments 21b
The position of 20b (shown by the solid line) is in contact with the arc-shaped pressing contact line (bottom line) B of the prior art or the pressing contact line B
The ring segments 21b are arranged so as to come to the outside of the.

FIG. 11 shows an embodiment in which the proportion of connection discontinuity of the pressing contact line (bottom line) 20b at the end of the ring segment 21b is reduced as compared with the embodiment of FIG. Also, unlike the embodiment of FIG. 10, the ring segment 21b is arranged so that the pressing contact line (bottom line) 20b goes in and out of the arc-shaped pressing contact line (bottom line) B of the prior art quite frequently. Are arranged.

FIG. 12 schematically shows the movement of the crushing roller 4 when the laterally displaced pendulum motion β of the crushing roller 4 is large. The behavior of the crushing roller 4 as described above is such that, under the condition that the compressed powder layer 18 is thin and the particle size is fine, the pressing contact line (lowermost line) 20b of the crushing ring 5 is shifted to the outside, particularly the ring segment 21b. It is more likely to occur when it comes around. On the other hand, FIG. 13 shows a case where the pendulum motion β of the crushing roller 4 is small, contrary to the embodiment of FIG. Even if the compressed powder layer 18 is thin and the grain size is fine, such a movement occurs when the pressing contact line (bottom line) 20b of the crushing race 17 is outside and when the pressing contact line 20a of the crushing roller 4 is inside (rotating). The case in the center of Table 3) and the case in which it is well combined occur.

If the movement shown in FIG. 12 and the movement shown in FIG. 13 occur at the same time in the same roller mill 1, the movements of the crushing rollers 4 are mutually restrained, and all the crushing rollers 4 have the same phase. Self-excited vibrations that move (synchronously) are almost completely suppressed.

Next, the segments 21a and 21b of the crushing section
By doing the above, the occurrence of self-excited vibration is prevented,
The results that can reduce the vibration level will be described.

FIG. 14 summarizes changes in the amplitude of vibration with respect to the amount of coal hold-up in the roller mill, targeting coal that is prone to relatively violent vibrations. The roller mill according to the embodiment (solid line) and the roller mill according to the prior art (broken line). )
It is a comparison of the amplitudes of and. The amplitude δoc on the vertical axis is
The crushing roller 4 and the crushing race 17 of the crushing ring 5 are made dimensionless by being divided by the amplitude δoc * when the metal touches and during idle rotation. On the other hand, the hold-up amount W on the horizontal axis is made dimensionless by dividing by the hold-up amount W * when the roller mill 1 is operated at the rated coal supply amount.

In the roller mill of the prior art, as shown by the broken line in FIG. 14, when the coal which is apt to vibrate relatively violently due to the influence of carbonaceous is crushed, the low load range (W / W * ~
0.38) significantly increases the amplitude, while the roller segment 21a and the ring segment 21 according to the embodiment
It can be proved from this test result that the roller mill 1 adopting b can significantly reduce the amplitude as shown by the solid line in FIG.

Even in the roller mill of the embodiment, the amplitude becomes slightly larger in the vicinity of W / W * to 0.38 than the other holdup conditions as shown by the solid line in FIG. 14, but this vibration is self-amplifying. This is not a self-excited vibration of a unique property, but a type of forced vibration in which the crushing roller 4 does not self-synchronize.

In this embodiment, the amplitude of the grinding roller 4 and the grinding race 17 of the grinding ring 5 is slightly larger than that of the roller mill of the prior art during idle rotation in which the grinding touches the metal touch. This is due to the irregular vibration caused by the different shapes of the segments 21a and 21b for each of the segments 21a and 21b. However, the level of this irregular vibration is slight and does not pose a problem.

FIG. 15 shows changes in the product fine particle size q with respect to the coal feed amount Qc. The particle size q on the vertical axis is expressed as a relative value by dividing by the standard fine powder particle size q in the conventional roller mill at the rated coal feed rate Qc. Qc on the horizontal axis is also divided by Qc * to make it dimensionless. Generally, the grain size q decreases with an increase in the coal supply amount Qc. In the roller mill according to the example, it was found that the product fine particle size (in FIG. 15) was almost the same as the particle size in the conventional roller mill (indicated by broken line in FIG. 15). That is, even if the shapes of the ring segment 21b and the roller segment 21a applied in the embodiment are changed, the crushing performance is not adversely affected.

[0055]

According to the present invention, vibration of the roller mill can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a roller mill according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a crushing unit of FIG.

FIG. 3 is an enlarged side view of a crushing roller.

FIG. 4 is a development view showing a segment of a crushing roller.

5 is a development view showing a segment of the crushing roller showing another embodiment of FIG. 4. FIG.

FIG. 6 is an enlarged cross-sectional view of the connection between the segments of the crushing roller.

FIG. 7 is a plan view showing a segment of a grinding ring.

FIG. 8 is a cross-sectional view of a grinding ring.

FIG. 9 is a plan view of a segment showing another embodiment of the grinding ring.

FIG. 10 is a plan view of a segment showing another embodiment of the grinding ring.

FIG. 11 is a plan view of a segment showing another embodiment of the grinding ring.

FIG. 12 is a diagram illustrating the movement of a crushing roller.

FIG. 13 is a diagram for explaining the movement of the crushing roller.

FIG. 14 is an amplitude characteristic curve diagram in which the vertical axis represents the dimensionless amplitude and the horizontal axis represents the dimensionless roller mill coal holdup amount.

FIG. 15 is a particle size characteristic curve diagram showing the fine powder particle size on the vertical axis and the non-dimensionalized coal feeding amount on the horizontal axis.

FIG. 16 is a schematic configuration diagram of a roller mill according to a conventional technique.

FIG. 17 is a diagram illustrating a support structure of a crushing roller and a swinging motion.

FIG. 18 is a diagram illustrating a support structure of a crushing roller and upward and downward movements.

FIG. 19 is a characteristic curve diagram showing non-dimensionalized amplitude on the vertical axis and non-dimensionalized coal hold-up in a roller mill on the horizontal axis.

[Explanation of symbols]

 3 Rotary table 4 Grinding roller 5 Grinding ring 20 Pressing contact line 21 Segment

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroaki Kanemoto 6-9 Takara-cho, Kure-shi, Hiroshima Babkotuku Hitachi Co., Ltd. Kure Factory (72) Hiroshi Yuasa 6-9 Takara-cho, Kure-shi, Hiroshima Babkotsu Hitachi Stock Company Kure Factory

Claims (1)

[Claims] 1. A crusher for crushing coal comprising a crushing roller, a crushing ring and a rotary table, wherein at least one of the crushing roller and the crushing ring is composed of a plurality of segments, and a pressing contact line is provided for each segment. Roller mill characterized by different.