JPH05317736A - Roller mill and manufacture of fine powder using the same - Google Patents

Abstract

PURPOSE:To provide a roller mill wherein a horizontal and vertical oscillation of a crushing roller is prevented and abnormal oscillation is avoided so that an operation under large area load or operation with a variety of coal can be performed. CONSTITUTION:A plurality of crushing rollers 4 are arranged symmetrically with respect to a center axis under urged state on a rotary table 3 rotatable about a vertical axis 19, and a raw material feed pipe 2 for feeding raw material 1 onto the table 3 is provided and an air throat 22, a rotary classifier 15, and a product fine powder delivery duct 24 are provided as a means to classify and take out crushed raw material, thereby forming a roller mill. Powder layer agitation blades 26 are provided on the side surface of the roller 4 on the side of the axis 19 of the rotary table to scrape up and agitate a raw material powder layer 20 on the table 3 in such a way that the number of these blades or fixing positions thereof with respect to the circumferential directions of the crushing roller are differentiated from each other at least for a plurality of crushing rollers.

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 a method for producing fine powder by a roller mill, and more particularly to a roller mill in which vibration under a low load is remarkably reduced and a method for producing fine powder by a roller mill.

[0002]

2. Description of the Related Art Even in a coal-fired boiler, low-pollution combustion (reduction of NOx, reduction of unburned content) and wide-area load operation have been carried out, and accordingly, a high-performance pulverized coal machine (mill) has been required. .. A vertical roller mill equipped with a rotary 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 or new raw materials. , Recently, it is solidifying its position as one of the representative models.

As shown in FIG. 1, this type of mill is driven by a motor (not shown) provided at the bottom of a cylindrical housing 14 (container) and equipped with a speed reducer, and rotates at a low speed on a horizontal plane. It is provided with a disc-shaped rotary table 3 and a plurality of crushing rollers 4 which are rotated by being hydraulically or pressurized by a spring or the like to positions at which the outer peripheral portion of the upper surface thereof is equally divided in the circumferential direction. The raw material supplied from the raw material supply pipe 2 (center chute) 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 rotary table. It is sandwiched between the upper crushing race 17 and the crushing roller and crushed. At the lower part of the housing, the hot air 21 sent in the duct 21
The hot air is blown up from the air throat 22 between the outer peripheral portion of the crushing table and the inner peripheral portion of the housing. The granular material generated by pulverization is dried while rising in the housing by the hot air blown from the air 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 therethrough is again detected by the cyclone separator or the rotary classifier 15 provided on the upper part of the housing. It is classified and sent to a pulverized coal burner or a pulverized storage bin in the 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. 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. The type of vibration 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. 12, 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 also occur at considerably high loads. is there.

FIG. 15 is a sectional view showing a supporting structure of a conventional grinding roller. In this type of roller mill, the crushing roller 1401 is swingably supported via a roller bracket 1402 with a roller pivot 1409 as a spindle. This swinging function is very important, and when the crushing roller 1401 bites in a foreign substance such as an iron piece that is difficult to be crushed, the crushing roller 1401 can avoid an impact by shaking its head. Further, when the crushing roller 1401 and the crushing race 1415 are worn, this swinging function also has the function of automatically finding an appropriate pressing position (positional relationship between the crushing roller 1401 and the crushing race 1415).

Generally, at the time of high load crushing, the crushing roller 14
01 almost does not shake his head. As mentioned above,
When the crushing roller 1401 actively engages the raw material when the mill is started or when the load increases, the crushing roller shakes its head, but the movements of the three crushing rollers are not synchronized in this swinging operation. At this time, the mill vibrates, but the dominant frequency cannot be specified because the crushing rollers 1401 are not synchronized, and the frequency distribution is broad, so-called forced vibration, and does not hinder the operation of the mill.

On the other hand, when the rollers vigorously vibrate by self-excitation, as shown in FIG. 13, all three grinding rollers 1201 laterally shift outward (β), and then vibrate vertically as shown in FIG. (Γ). The three grinding rollers vibrate up and down together synchronously (in phase). When a certain crushing roller causes a lateral displacement-like swinging motion (β) and vertical vibration of the crushing roller occurs, this movement is caused by the integral pressing frame 11 (FIG. 1) or rotary table 1206 common to each crushing roller. And the powder layer on it and propagate to other grinding 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. Based on the above idea, the object of the present invention is to prevent the crushing roller from oscillating its head or oscillating up and down, and to enable operation in a wide area load or a multi-carbon type without causing abnormal vibration. The purpose is to provide a roller mill.

[0009]

To achieve the above object, the first invention of the present application is to provide a rotary table which rotates about a vertical axis, and a plurality of rotary tables which are arranged on the rotary table and are pressed and rotated according to the rotation of the rotary table. In a roller mill provided with a crushing roller, a raw material supply pipe for supplying a raw material onto a rotary table, and means for classifying the crushed raw material to take out fine powder particles, a vertical axis of a rotary table of one or more crushing rollers. The present invention relates to a roller mill characterized in that a powder layer stirring blade for scraping up and stirring a raw material powder layer on a rotary table is provided on the side surface on the side.

According to a second invention of the present application, in the first invention, the number of the powder layer agitating blades or the disposition position of the crushing rollers in the circumferential direction is different in at least a plurality of crushing rollers. Regarding the roller mill. According to a third aspect of the present invention, a rotary table is rotated about a vertical rotation axis, and a plurality of pulverizing rollers are arranged in a symmetrical position on the rotary table with respect to the vertical rotation axis in a pressurized state to rotate the rotary table. In the method for producing fine powder by a roller mill that rotates and supplies the raw material onto the rotary table and pulverizes the raw material powder layer on the rotary table by the powder layer stirring blade provided on the side surface of the rotary table vertical axis side of the pulverizing roller. The present invention relates to a method for producing fine powder by a roller mill, which comprises crushing raw materials with a crushing roller and a rotary table while stirring and stirring.

[0011]

Since the flow of the powder layer on the rotary table is irregularly disturbed by the powder layer agitating blade installed on the pulverizing roller, the state of the powder layer biting of the pulverizing roller also varies irregularly for each pulverizing roller. become. By such an action, it is possible to prevent the self-excited vibration of the roller mill that "the crushing roller is synchronized, that is, the head is shaken so as to be laterally displaced in the same phase, and further vertically synchronized." For example, one of the three grinding rollers
Even if the head is shaken so as to be laterally displaced due to the collapse of the powder layer under the grinding roller, the other two grinding rollers have a biting state different from that of the grinding roller to which the head is sprinkled, because the other two grinding rollers are different from each other. Does not follow the swing motion. As a result, the vibration-triggering movement of the crushing roller on which the head is sprung is canceled by another crushing roller which does not follow the vibration.

On the other hand, when one crushing roller vibrates, the powder layer on the crushing race swells (the thickness changes periodically), which is a self-exciting system (feedback loop).
May be formed. However, according to the present invention, the powder layer stirring blade irregularly supplies the powder layer onto the wavy powder layer, and the so-called "cycle" of the powder layer due to vibration is destroyed. In this way, the powder bed stirring blade according to the present invention has a self-excited system (feedback loop) in self-excited vibration.
And acts to suppress severe self-excited vibration.

[0013]

The features of the present invention reside in the structure of the crushing roller, which will first be described and the overall structure of the mill will be described later. FIG. 2 shows the structure of one crushing roller installed in a roller mill embodying the present invention.
The raw material powder layer (not shown in the figure) on the rotary table 208 is scraped up inside the crushing roller 201, that is, on the side surface 205 of the rotary table 208 in the direction of the rotary shaft 207, and at a position close to the crushing surface 206. One powder layer agitating blade 203 for agitating the powder with the rotation of the pulverizing roller 201 is provided. The powder layer stirring blade 203 has a shape that is slightly curved in the rotational direction so that the powder layer can be easily lifted up.

FIG. 3 shows the arrangement positions of the powder layer agitating blades in the three pulverizing rollers in the roller mill. This figure is developed as a plan view in the circumferential direction of the rotary table so that the side surface 305 of the crushing roller 301 is seen from the central axis side of the rotary table. Laura (a)
As shown in FIG. 2, one powder layer stirring blade 303a is provided at 301a. The roller (b) 301b has two powder layer stirring blades 303b (1) and 303b.
(2) are provided in a state of being close to each other and separated by a rotation angle of 90 °. However, the "complementary angle" with respect to the circumferential direction of 90 ° is 270 ° C. Based on this complementary angle, the powder layer stirring blade 303b in this roller is used.
This means that (1) and 303b (2) are provided far apart. The roller (c) 301c includes three powder layer stirring blades 303c (1), 303c (2) and 30.
3c (3) is provided. Powder layer stirring blade 303
c (3) and 303c (2), and 303c (2) and 3
03c (1) is 90% in the circumferential direction of the crushing roller.
The powder layer agitating blade 303c is arranged at a distance of °
The positions (1) and 303c (3) are 180 ° apart from each other. As described above, in the roller mill using the three pulverizing rollers shown in FIG. 3, since the number of powder layer agitating blades is different for each pulverizing roller, the agitating of the powder layer on the rotary table results in In this case, the state of the powder layer biting of each crushing roller becomes irregular.

In FIG. 4, the number of powder layer stirring blades installed is 2
Although two crushing rollers are the same for both crushing rollers, the method of arranging the two crushing rollers is different for each crushing roller.
In the crushing roller 401 (a), two powder layer stirring blades 403a (1) and 403a (2)
It is provided at a distance of 90 ° with respect to the circumferential direction of (a) (270 ° at the “complementary angle” on the opposite side). Crushing roller 4
With powder layer stirring blades 403b (1) and 403b (2) in 01 (b), 30 ° (330 ° with "completion")
Are arranged at intervals. 2 of crushing roller 401 (c)
Powder layer stirring blades 403c (1) and 403c (2)
Are provided at equal intervals of 180 °. Even in the roller mill using three crushing rollers as in this example, the state of the powder layer supplied to the crushing rollers is different for each crushing roller because the stirring state of the raw material powder layer on the rotary table becomes irregular. It will be.

The crushing roller 501 shown in FIG. 5 has a part of a side surface 506 of the rotary table 507 in the direction of the central axis 508.
In this example, eight powder layer stirring blades 503 are brought close to each other and arranged in a row. FIG. 6 is an example in which a plurality of powder layer stirring blades 603 are arranged in a row in each of the three crushing rollers 601a, 601b and 601c in the roller mill, similarly to the crushing roller shown in FIG. However, the number of powder layer stirring blades 603, that is, the blade rows 604 (a), 604 (b) and 60
In order to make the flow of the powder layer on the rotary table irregular by varying the length of 4 (c) (with respect to the circumferential direction of the crushing roller) and changing the stirring ability for the powder layer for each crushing roller. It was done.

Here, the overall structure (FIG. 1) of the roller mill equipped with the crushing roller according to the present invention will be described. The 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 rotating at the lower part of the mill. A centrifugal force acts on the pulverized raw material powder layer 20 on the rotary table 3 and the centrifugal force is supplied to the pulverized ring 16 on the outer periphery of the rotary table 3 to generate the pulverized ring 1.
Grinding race 1 engraved on the upper surface of 6 and having a substantially arc-shaped cross section
7 is crushed and compressed by the crushing roller 4. As described above, on the inner side surface of the crushing roller 4, the powder layer stirring blade 26 for stirring the crushing raw material powder layer on the rotary table 3 is provided. The pulverized powder is penetrated between the air throats 22 and dried by the hot air 21 blown into the mill, while being transported to the upper side 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 classifying portion is centrifugally classified by the rotary classifier 15 (secondary classification). The relatively coarse particles are blown to the inner wall of the mill housing 14 by centrifugal force, and are dropped by gravity to be reground. The fine particles penetrate between the blades of the rotary classifier 15 and serve as product fine powder as a product fine powder discharge duct 2
Emitted from No. 4. In the case of coal, it is directly sent to the fine powder burner (the hot air 21 becomes the primary air for combustion) or is collected in the storage bin.

In FIG. 7, although the raw material powder layer is omitted,
The powder layer on the rotary table 717 is removed by the crushing roller 71.
1 schematically shows how a powder layer stirring blade 712 provided on the inner side surface 718 of No. 1 lifts up and stirs the powder layer. FIG. 8 schematically shows the positional relationship when the powder layer stirring blade 725 scrapes up the powder layer 726. In this example, since the number of powder layer stirring blades and the arrangement condition in the circumferential direction of the crushing rollers are different for each crushing roller, the stirring state of the powder layer is irregular. That is, in the left grinding roller,
The powder layer is agitated once by rotation with three powder layer stirring blades. On the other hand, in the crushing roller on the right side, the powder layer stirring blade row composed of two blades and three blades respectively (see FIG. 7) stirs the powder layer twice. Therefore, the flow state of the raw material powder layer on the rotary table 717 becomes irregular. In this way, the state of biting of the powder layer by the crushing rollers differs for each crushing roller, so that the crushing rollers do not move in synchronization (in phase). Even if one crushing roller swings its head so as to skid, the other crushing rollers do not synchronize with the skid-like swinging motion because the powder layer has a different biting state from the crushing roller. .. In this way
It is possible to prevent the violent self-excited vibration in which the three crushing rollers shake the head synchronously and further vertically vibrate synchronously.

On the other hand, let us consider a case where self-excited vibration is about to occur, changing the viewpoint. As shown in FIG. 8, the crushing roller 721 vibrates vertically. When one crushing roller vibrates up and down in this way, the powder layer 726 on the crushing race 724 has a wavy state (broken line in the figure) 7β due to the compression action when the roller periodically drops. Like On the other hand, if the powder layer stirring blade 725 according to the present invention forcibly stirs the powder layer 726 and raises it,
The powder layer 7γ becomes as shown by the solid line in the figure, and the “waviness” in the powder layer disappears as it is filled. This "ripple" in the powder layer is the feedback loop that forms a self-excited system in self-excited vibration. Therefore, the use of the powder bed agitating blade according to the present invention produces the effect of breaking the feedback loop of the crushing section that forms the self-excited system. In this way, amplification of self-excited vibration is prevented, and as a result, self-excited vibration is quickly decelerated.

FIG. 9 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 δ _{0C on the} vertical axis is
It is made dimensionless by dividing by the amplitude δ _0C ^* during metal touch (idle rotation without coal). 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 liable to vibrate relatively violently due to the influence of coal quality. In the conventional technology, the amplitude is remarkably large at a low load (W / W ^* to 0.38), whereas the roller mill equipped with the pulverizing roller to which the powder layer stirring blade according to the present invention can significantly reduce vibration. It was proved that. Even in the roller mill using the pulverizing roller provided with the powder layer stirring blade according to the present invention, W / W ^* to 0.
Although the amplitude becomes slightly larger at 38, this vibration is considered to be one type of forced vibration. In the embodiment of the present invention, the amplitude during idle rotation (metal touch) is almost the same as that in the prior art. This is because the powder bed stirring blade according to the present invention has nothing to do with the metal touch rotation of both grinding surfaces of the grinding roller and the grinding race.

FIG. 10 is a summary of the results when coal which is not so violent even when the roller mill vibrates is used. Also in this example, it can be seen that the amplitude can be reduced by embodying the present invention. FIG. 11 shows a change in the product fine powder particle size q with respect to the coal supply amount Q _C. Particle size q of the vertical axis is represented as a relative value is divided by the reference fine granularity q ^* in a conventional mill at a nominal coal feed amount Q _C ^*. The value on the horizontal axis is also divided by Q _c ^* to make it dimensionless. Generally, particle size q decreases with increasing Kyusumiryou Q _c. In the examples according to the present invention, it has been found that the particle size of the product fine powder is almost the same as that of the conventional roller mill. That is, the stirring of the powder layer by the powder layer stirring blade in the pulverizing roller of the degree embodied in the present invention,
It is considered that the crushing performance is not significantly affected (at least it does not deteriorate the crushing performance).

The roller mill equipped with the crushing roller having the structure according to the present invention is not limited to the mill for coal-fired boilers described as a specific example. (I) Mill for oil coke which is the same solid fuel (ii) Desulfurization Mill for finely crushing limestone for industrial use (iii) Mill for finely crushing iron and steel or non-ferrous slag (IV) Mill for finely crushing cement curriculum (V) Finely pulverize raw materials for various chemical products It can be applied to a mill almost as it is.

[0023]

The effects of the mill adopting the grinding roller embodying the present invention are summarized as follows. (1) It is possible to prevent the vibration of the mill due to the sliding of the roller on the powder layer. This improves the durability of various peripheral devices including the mill itself. As a result, the reliability of the entire plant including the mill is increased. (2) Low load operation becomes possible, and the minimum load of the mill can be further reduced. This will expand the operating range of plants such as boilers that use mills. Since it is possible to burn coal in a low-load operation area of the boiler, it is possible to reduce the amount of fuel oil for combustion support. Therefore, the entire thermal power plant can be operated more economically. (3) Vibration can be avoided even with various pulverized raw materials. In this way, the types of coal applicable to thermal power plants will be greatly expanded, and a wider range of multi-coal species operations will become possible.

[Brief description of drawings]

FIG. 1 is an internal schematic diagram of a roller mill to which the present invention is applied.

FIG. 2 is a diagram showing a crushing roller provided with a powder layer stirring blade according to the present invention.

[Fig. 3]

[Fig. 4]

FIG. 5 and

FIG. 6 is an embodiment diagram showing attachment and arrangement of a powder layer stirring blade to a pulverizing roller.

[FIG. 7]

FIG. 8 is a view showing a powder layer stirring state of the pulverizing roller according to the present invention.

FIG. 9

FIG. 10 and

FIG. 11 is a diagram showing the effect of the present invention.

FIG. 12

FIG. 13 and

FIG. 14 is a diagram showing a problem of the conventional technique.

FIG. 15 is a structural diagram of a crushing roller of a conventional roller mill.

[Explanation of symbols]

1 ... Raw material, 2 ... Raw material supply pipe, 3 ... Rotary table, 4 ... Grinding roller, 5 ... Roller bracket, 6 ... Roller rotation shaft,
9 ... Pivot box, 10 ... Roller pivot, 11 ...
Pressure frame, 12 ... Spring, 13 ... Spring frame, 14 ... Housing, 15 ... Rotation classifier, 16 ...
Grinding ring, 17 ... Grinding race, 18 ... Compressed powder layer, 19
... table rotary shaft, 20 ... ground material powder layer, 21 ... hot air,
22 ... Air throat, 24 ... Product fine powder discharge duct, 26
… Powder layer stirring blade.

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

Claims (3)

[Claims] 1. A rotary table which rotates about a vertical axis, a plurality of crushing rollers which are arranged on the rotary table under pressure and rotate according to the rotation of the rotary table, and a raw material supply pipe for supplying a raw material onto the rotary table. In a roller mill provided with means for classifying the crushed raw material and taking out fine powder particles, a powder for scraping and stirring the raw material powder layer on the rotary table on the side surface of one or more crushing rollers on the vertical axis side of the rotary table. A roller mill provided with a layer stirring blade. 2. The roller mill according to claim 1, wherein the number of the powder layer agitating blades or the arranging positions of the crushing rollers in the circumferential direction are different among at least a plurality of crushing rollers. 3. A rotary table is rotated about a vertical rotary shaft, and a plurality of crushing rollers are arranged in a pressurized state at symmetrical positions with respect to the vertical rotary shaft on the rotary table and are rotated by rotation of the rotary table. In a method for producing fine powder by a roller mill that feeds and pulverizes a raw material on the rotary table, a raw material powder layer on the rotary table is agitated by a powder layer stirring blade provided on the side surface of the pulverizing roller on the vertical axis side of the rotary table. A method for producing fine powder by a roller mill, characterized in that the raw material is crushed by a crushing roller and a rotary table.