JPH0699093A - Roller mill and grinding method by roller mill - Google Patents

Abstract

PURPOSE:To prevent strong self-excited vibration generated in a low load region by providing any of a projected part, a recessed part and a braid member on the surface of a conic form installed in the central part of the upper surface of a turntable irregularly to the circumferential direction of the table and making irregular the feed quantity of a raw material to each grinding roller falling on the pyramid. CONSTITUTION:A pyramid is installed in the central part of the upper surface of a turntable 11 and a grinding groove 13 is made along the periphery of the table 11 and plural grinding rollers 1 are arranged on the surface of the grinding groove 13 and a feeder 25 for raw material is provided on the conic form. In the roller mill, any one or more of a projected part, a recessed part and a braid member are arranged on the surface 11a of the conic form irregularly to the circumferential direction of the tuntable 11. Raw material falls to the conical form to make irregular the feed quantity of the raw material to each grinding roll 1. As a result, strong self-excited vibration mainly generated in a low load region is prevented and the operating load range of plants using a mill, such as a boiler is widened.

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 grinding method using a roller mill, and in particular, the supply amount of raw materials to a plurality of grinding rollers on a rotary table is irregular in the circumferential direction to suppress vibration during operation. And a pulverizing method by the roller mill.

[0002]

2. Description of the Related Art In a coal-fired boiler, combustion (low NOx, low unashed content in low ash) that does not emit harmful substances to the environment and wide-area load operation are performed, and the pulverized coal machine (mill) also has high performance. Is required. As one type of mill that grinds lumps such as coal, cement raw materials or new raw materials
A vertical roller mill that grinds with a rotating table and a plurality of rollers has been widely used, and recently, it has been solidifying its 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 an electric motor to rotate at a low speed through a speed reducer, and a circular table on the upper surface of the outer peripheral portion of the table. It is provided with a plurality of crushing rollers that rotate by being hydraulically pressed or pressed by springs or the like to positions equally divided in the circumferential direction. The raw material to be pulverized, which is supplied from the chute to the center of the table, moves to the outer periphery of the table while drawing a spiral trajectory on the table by centrifugal force, and is crushed by being caught between the crushing race and the crushing roller of the table. It Hot air is guided to the lower part of the mill housing through a duct, and the hot air is blown up from an air throat between the rotary table and the housing. The crushed powder 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 material by gravity (primary classification) and is re-pulverized in the pulverization section. The slightly 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. Coarse particles having a predetermined particle size or more, which have not passed through the classifier, are dropped by gravity onto the rotary table and are crushed again together with the raw material (coal coal) just supplied into the mill. In this way, the pulverization is repeated in the mill to produce fine product powder.

There are various shapes of the rotary table in such a roller mill. As shown in FIG. 16, there are a mill having a center cone 1418 having a gentle apex angle in the center of the rotary table 1412 and a mill having a center cone 1501 having a sharp apex angle as shown in FIG. On the other hand, in the example of FIG. 18 (product example: Ube Roche Mill), the rotary table 1601 has a flat plate shape, and the rollers 1603 also rotate on the outer periphery of the flat plate table. Further, there is a type of mill (product example: Mitsubishi-CE bawl mill) that has a flat plate-like table but has an inclination on its outer periphery and presses a roll there. In this mill, the rotary table is called a bowl because it is a bowl type. The structure of this baul mill is shown in FIG.

[0005]

When the roller mill is to be operated under a low load, the vibration of the mill is a problem in reducing the load. This vibration phenomenon is complicated and the detailed mechanism is not clarified, but a kind of frictional vibration (stick / slip motion known as representative of discontinuous / non-linear vibration) caused by the slip between the coal bed and the roller. Is believed to be. As the type of vibration, it can be said to be a kind of self-excited vibration because the excitation source cannot be clearly specified and the vibration waveform has a spike shape. With normal coal, as shown in Fig. 13, the vibration of this mill 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. There is.

FIG. 16 is a sectional view showing a supporting structure of a conventional grinding roller. In this type of roller mill, the crushing roller 1401 is supported via a roller bracket 1403 so as to be swingable about a roller pivot 1408 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 1414 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 1414).

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 vigorously bites the raw material at the time of starting the mill or increasing the load, the crushing roller 1401 shakes its head.
The movements of the individual grinding rollers are not synchronized. At this time, the mill vibrates, but because the crushing roller 1401 is not synchronized, the dominant frequency cannot be specified, and the frequency distribution is broad, so-called forced 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. 14, 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 (γ) of the crushing roller occurs, this movement is integrated by a pressure frame that pressurizes three crushing rollers. It propagates to the other crushing rollers through the pressure frame of the body or the rotary table and the powder layer on it. 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 concept, a roller mill that prevents the crushing roller from oscillating its head or vibrates up and down, and enables operation in a wide area load or in a multi-carbon type without causing vibration. Another object of the present invention is to provide a grinding method by a roller mill.

[0010]

In order to achieve the above object, the first invention of the present application is a rotation that is rotated by a driving device and that has a cone provided at the center of the upper surface and a grinding groove surface along the outer circumference. In a roller mill provided with a table, a plurality of crushing rollers arranged on the crushing groove surface of the rotary table, and a raw material supply device for supplying the raw material to be crushed onto the rotary table cone, the roller mill is dropped on the cone. The protrusions on the surface of the cone, so that the amount of raw material supplied to each crushing roller is irregular,
The present invention relates to a roller mill in which at least one of a recessed portion and a blade-shaped member is arranged irregularly in a circumferential direction of a rotary table.

A second invention of the present application is the same as the first invention, wherein the protrusion, the depression or the blade member is
The pyramid was radially formed from the apex of the cone toward the outer peripheral edge of the cone, and the height of the protrusion, the depth of the recess, or the height of the blade member was configured to be larger toward the outer periphery of the cone. The present invention relates to a roller mill. A third invention of the present application is the raw material granule to be crushed according to the first or second invention, wherein the maximum height of the protrusion, the maximum depth of the recess or the maximum height of the blade-like member at the lower end of the cone is defined. The present invention relates to a roller mill characterized in that the maximum particle size is at least 3 times or more.

According to a fourth aspect of the present invention, a rotary table having a cone provided in the central portion of the upper surface and a crushing groove surface provided along the outer peripheral portion is rotated by a driving device, and the rotary table has a cone. In the method of pulverizing the raw material by a roller mill in which the raw material to be pulverized is supplied and pulverized by a plurality of pulverizing rollers arranged on the pulverizing groove surface of the rotary table, the rotary table is a protrusion on the cone surface of the central portion of the upper surface, Using a rotary table in which at least one of the recessed portion or the blade-like member is irregularly arranged in the circumferential direction, the raw material to be crushed is supplied to the crushing roller so as to be irregular in the circumferential direction of the rotary table. The present invention relates to a pulverizing method using a roller mill.

[0013]

The rough raw material supplied from the chute or the fine particles circulated from the classifying portion flows radially outward along the protrusions or depressions of the conical surface on the rotary table. The state of the flow of the raw material supplied to the biting part of the crushing roller varies depending on the shape of the protrusion or the depression. The raw material on the protrusion flows like falling, and fine powder easily flows into the bottom of the recess. In this way, the flow state of the raw material due to the rotation of the rotary table becomes irregular. This means that the protrusions or depressions are arranged irregularly in the circumferential direction of the turntable. According to the present invention, when the coal layer in the crushing section of the mill is in a state where self-excited vibration is likely to occur, the supply of the raw material becomes irregular, and a plurality of crushing rollers are synchronized (with the same phase). In this case, the self-excited vibration as a so-called self-synchronization phenomenon, which shakes the head so as to laterally shift and then vibrates in the vertical direction, is prevented. Even if the compressed powder layer under one of the crushing rollers collapses and the head is shaken so that it shifts laterally, the other crushing rollers are crushed by the crushing roller whose supply state of the raw material to the biting part Since it is different from that in the section, it does not synchronize with the swinging motion.
That is, a slight difference in the supply state of the raw material in the biting portion of each crushing roller has the effect of canceling the swinging motion of the crushing roller.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the structure of a roller mill equipped with a rotary table having a shape embodying the present invention as a sectional view passing through a central axis. The crushing unit of this roller mill is composed of the crushing roller 1 and the rotary table 11. A crushing ring 12 having a substantially arc-shaped crushing race 13 engraved on the upper surface is attached to the outer edge of the rotary table 11 in the radial direction. The raw material 24 (coal in the case of a roller mill for a coal-fired boiler) is It is compressed between the crushing roller 1 and the crushing race 13 and crushed. The central portion of the rotary table 11 has a gentle conical shape having an apex on the table rotary shaft 14. The present invention relates to this rotary table 1
Since it relates to the shape of the central portion of No. 1, it will be explained first.

FIG. 2 shows the shape of the conical portion in the center of the rotary table (which will be referred to as the center cone) embodying the present invention. Center cone 201
On the slope, there is provided a center cone recess 202 whose starting point 202a is the apex of the center cone 201 (which is on the rotation center axis 203) and whose width and depth increase as it goes down the slope. The bottom of the center cone recess 202 is sharp and has a triangular cross section.

The center cone 301 is shown in FIG.
This is an example in which the starting point is the apex of the center cone 301 and the center cone convex portion 302 whose width and height increase along the slope is provided on the upper slope. Also in this example, FIG.
Similar to the example of FIG. 3, the origin of the center cone convex portion 302 is on the rotation center axis 303. This center cone protrusion 30
2 has a shape that is rounded upward.

In the example shown in FIG. 4, the powder layer on the rotary table is forcibly stirred as the rotary table rotates,
This is the case where the blade 305 is provided on the slope of the center cone 304. Also in this blade, the starting point 305a is aligned with the apex of the center cone 304 on the rotation center axis 306. In each of the above-mentioned three examples, the representative dimension of the concave portion, the convex portion or the lower end of the blade located at the bottom edge of the center cone portion, that is, the maximum depth d _M of the center cone concave portion (FIG. 2), the center cone convex portion Maximum height h _M (Fig. 3) or maximum blade height h _M (Fig. 4)
Is configured to be at least 3 times the maximum particle size of the pulverized raw material. This is because it produces an effect of disturbing the raw material powder layer flowing down the center cone portion such as stirring.

FIGS. 5, 6 and 7 show an example of arrangement of the center cone convex portion and the center cone concave portion on the rotary table. The example of FIG. 5 is an example in which two center cone convex portions 402 and two center cone concave portions 403 are irregularly arranged in the circumferential direction of the rotary table 405. Figure 6
Also in the example of, the center cone convex portion 502 is similar to the example of FIG.
Two center cone concave portions 503 are arranged, but the arrangement order is different from the example of FIG. In the example shown in FIG. 7, four center cone convex portions 602 and three center cone concave portions 603 are arranged on the rotary table 605 irregularly in the circumferential direction.

Although the order is reversed, the entire structure of the roller mill equipped with the rotary table according to the present invention will now be described (FIG. 1).
Will be described. The raw material 24 is supplied from a raw material supply pipe (center chute) 25 located on the central axis of the upper part of the mill, and drops onto the rotary table 11 rotating at the lower part of the mill. Centrifugal force acts on the raw material powder layer 15 on the rotary table 11, is supplied onto the crushing ring 12 on the outer periphery of the rotary table 11, is crushed on the upper surface of the crushing ring 12, and has a substantially arc-shaped cross section. Crushing roller 1 on race 13
1 is compressed and crushed. As described above, in the present invention, the central portion of the rotary table 11 is formed of a gentle conical body, and either or both of the center cone convex portion 11a and the center cone concave portion 11b are provided on the slope of the conical body. The rotary table 11 is arranged irregularly in the circumferential direction. The pulverized powder is passed through the throat vanes 17 and is dried by the hot air 19 blown into the mill while being transported to the upper side of the mill. The coarse particles fall on the rotary table 11 due to gravity (primary classification), and are crushed again in the crushing section. The particle group penetrating this primary classification part is centrifugally classified by the rotary classifier 21 (secondary classification). The relatively coarse particles cannot pass through here and fall below the mill, the fine powder penetrates between the blades of the rotary classifier 21, and is discharged from the product fine powder discharge duct 23 as product fine powder. In the case of coal, it is sent directly to the pulverized coal burner (hot air 19 becomes the primary air for combustion) or is collected in a storage bin.

FIG. 8 and FIG. 9 show (a) a side view and (b) a view from above, respectively, when the raw material is fed from the convex portion of the center cone and the concave portion of the center cone toward the crushing roller. Show as. FIG. 8 shows a state in which the position of the convex portion of the center cone provided on the rotary table 713 exactly coincides with the position of the crushing roller 711. The crushing raw material 719 is supplied from the upper part of the center cone convex part 717 to the biting part of the crushing roller 711, and as shown in (b) the upper view, it flows down from the upper part of the center cone convex part 717. (719a) and is bitten into the crushing roller 711. For example, consider the case where relatively coarse raw material particles are bitten into a grinding roller. The coarse material particles fall from the tip of the convex portion of the center cone to the position of the crushing roller (in the case of the convex portion, the tip is the highest as described above), or the lowest portion of the concave portion of the center cone (the tip of the concave portion is the tip). Is the lowest part), and the behavior of the roller (the state of lift and swing of the roller) varies depending on whether or not it is supplied to the crushing roller. FIG. 9 is a schematic drawing of an aspect in which the positions of the crushing roller 721 and the center cone recess 727 are aligned. The crushing raw material 729 is made to flow into the center cone concave portion 727 from the periphery (729a), and the crushing roller 7
21 is supplied. In the case of the center cone concave portion 727, unlike the case of the center cone convex portion of FIG. 8, the crushing raw material 729 is supplied through the center cone concave portion in a state in which the crushing roller 721 is relatively easily bited. When coarse raw material particles are supplied from the tip of the convex portion of the center cone as shown in FIG. 8 (close to "falling" as a phenomenon), the crushing roller is less likely to bite than in the case of the concave portion of the center cone. Conceivable.

As described above, the biting state of the crushing roller changes depending on the supply state of the raw material to the crushing roller.
By the rotation of the rotary table, the biting state of the crushing roller changes irregularly according to the positions of the center cone convex portion and the center cone concave portion. Therefore, the lift and swinging state of the crushing roller also change irregularly. For example, of the three grinding rollers in the mill, even if the compressed powder layer under one grinding roller collapses and the grinding roller suddenly shakes its head (this causes self-excited vibration) , The other crushing rollers do not follow this swinging motion. Eventually, this swinging motion will be canceled by the irregular movement of the other grinding rollers. By such an action, it is possible to prevent the occurrence of a so-called self-synchronization phenomenon (the self-excited vibration in which this phenomenon is amplified) in which three grinding rollers swing in synchronization (in the same phase) and vibrate vertically. become able to. As the rotary table rotates, the operation of the crushing rollers also changes irregularly at all times due to the influence of the irregularly arranged center cone projections or recesses on the crushing rollers. As a result, especially when the mill is operated under a low load, the mill always vibrates, but this vibration is a weak forced vibration that is not amplified and does not hinder the operation of the mill. As described above, the self-excited vibration of the roller mill is prevented, the reliability of the mill is improved, and the operation capability is significantly improved.

FIG. 10 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 on the vertical axis
_0C is amplitude δ _0C at 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 apt to cause relatively violent vibration due to the influence of coal quality. In the prior art, the amplitude is remarkably large at a low load (W / W ^* ≈0.38), whereas the roller mill equipped with the rotary table having the shape according to the present invention can significantly reduce the amplitude. It was proven. Even when the rotary table according to the present invention is used, W /
Although the amplitude slightly increases at W ^* ≈0.38, this vibration is considered to be one type of forced vibration, not self-excited vibration having a self-amplifying characteristic. In the embodiment of the present invention, the amplitude during idling (the roller and the race touch the metal) is almost the same as that in the prior art. This is because the structure of the rotary table according to the present invention has nothing to do with the metal-touch rotation of both the crushing surfaces of the crushing roller and the crushing race.

FIG. 11 is a summary of the results when coal is used, which is not so violent when the roller mill vibrates. Also in this example, it can be seen that the amplitude can be reduced by embodying the present invention. 12
Shows the 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 made dimensionless by dividing by Q _c ^* . Generally, the grain size q is the amount of coal supply Q _c
Decreases with increasing. In the examples according to the present invention, it was found that the product fine particle size was almost the same as that of the conventional roller mill. That is, it is considered that the change in the supply state of the raw material powder layer due to the shape of the rotary table as embodied in the present invention does not significantly affect the pulverizing performance (at least does not reduce the pulverizing performance).

The roller mill adopting the rotary table having the structure according to the present invention is not limited to the mill for coal-fired boiler described as the specific example, but (i) a 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 steel slag or non-ferrous refining slag as a raw material for cement or refractory (IV) Mill for cement finishing to finely crush cement clinker (V) Various types It can be applied almost as is to a mill that pulverizes raw materials for chemical products.

[0025]

The effects of implementing the present invention are summarized as follows. (1) Vibration of the mill can be prevented. (2) Due to the effect of (1) above, the reliability and durability of the mill itself and the plant-related equipment around the mill are improved. Further, the discomfort felt by the employees in the plant is eliminated, and the work efficiency is improved. (3) Vibration can be suppressed in the low load zone, so wide load operation of the entire boiler is possible, not limited to the mill. (4) Specific coal species and solid fuels, which have been feared to be susceptible to vibration, can be used without problems. This greatly expands the applicability of the milling material to the mill.

[Brief description of drawings]

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

[Fig. 2]

FIG. 3 and

FIG. 4 is a diagram showing an embodiment of protrusions, depressions, and blade-shaped members provided on the surface of the cone of the rotary table in the present invention.

[Fig. 5]

FIG. 6 and

FIG. 7 is a layout view of protrusions and depressions provided on the surface of a rotary table cone.

FIG. 8

FIG. 9 is a view showing a raw material supply state with respect to a crushing roller in the roller mill according to the present invention.

FIG. 10:

FIG. 11 and

FIG. 12 is a diagram showing a vibration suppressing effect and a pulverizing performance in the roller mill when the present invention is applied.

FIG. 13

FIG. 14 and

FIG. 15 is a diagram showing a vibration phenomenon in a conventional roller mill.

FIG. 16:

FIG. 17:

FIG. 18 and

FIG. 19 is a view showing a rotary table of a conventional roller mill.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Grinding roller, 5 ... Roller bracket, 7 ... Roller pivot, 8 ... Pressure frame, 11 ... Rotary table, 11
a ... Cone surface (center cone) convex portion, 11b ... Cone surface (center cone) concave portion, 14 ... Rotating table rotating shaft, 15 ... Raw powder layer, 16 ... Compressed powder layer, 20 ... Mill housing, 21 ... Rotation Classifier, 24 ... Raw material, 25 ... Raw material supply pipe, 305 ... Blade.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tadashi Hasegawa 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Ltd. Kure Factory (72) Hiroaki Kanemoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Stock Company Kure Factory (72) Inventor Yoshinori Taoka 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory (72) Inventor Hiroshi Yuasa 6-9 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Factory

Claims (4)

[Claims] 1. A rotary table which is rotated by a driving device and has a cone provided in the central portion of the upper surface and a grinding groove surface along the outer circumference, and a plurality of grinding rollers arranged on the grinding groove surface of the rotary table. In a roller mill provided with a raw material supply device for supplying the raw material to be crushed onto the rotary table cone,
At least one of a protrusion, a depression, and a blade member is provided on the surface of the cone so that the amount of raw material supplied to the crushing rollers by dropping on the cone is irregular. A roller mill characterized by being arranged irregularly in the circumferential direction. 2. The protrusion according to claim 1, wherein the protrusion, the depression, or the blade-like member is formed radially from the apex of the cone toward the lower outer peripheral end of the cone, and the height of the protrusion and the depression. The roller mill is characterized in that the depth of the blade or the height of the blade member is increased toward the outer circumference of the cone. 3. The maximum height of the projection, the maximum depth of the recess, or the maximum height of the blade member at the lower end of the cone is defined as at least the maximum particle size of the raw material granules to be crushed according to claim 1 or 2. A roller mill characterized by being tripled or more. 4. A rotary table having a cone provided in the center of the upper surface and a crushing groove surface provided along the outer periphery is rotated by a drive device to supply the raw material to be crushed onto the cone of the rotary table. Then, in the pulverizing method of the raw material by the roller mill for pulverizing by the plurality of pulverizing rollers arranged on the pulverizing groove surface of the rotary table, as the rotary table, the projection surface, the hollow portion or the blade-shaped member on the cone surface of the central portion of the upper surface. A roller mill characterized by using a rotary table in which any one or more of them is irregularly arranged in the circumferential direction, and feeding the material to be crushed to the crushing roller so as to be irregular in the circumferential direction of the rotary table. Grinding method.