JPH1099701A - Roller mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a stable operation without self-excited vibration in the wider range with respect the rotation speed of a rotating classifier so as to form fine particles of good grading. SOLUTION: A roller mill has a rotary table 3 rotating around the vertical axis of the mill below in a mill housing, a grooved pulverizing part 2 provided on the outer peripheral part of the rotary table 3, and plural pulverizing roller 4 rotating at a position at which the upper surface is equally divided in the circumferential direction. In this case, on the grooved pulverizing part 2 of the rotary table 3, a first pulverizing part 21 on the inner peripheral side and a second pulverizing part 22 on the outer peripheral side are provided so that a gap between the rotary table 3 and the pulverizing rollers 4 may be wider on the outer pulverizing part than on the inner pulverizing part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying coal, cement clinker, and other granular or block-shaped raw materials onto a rotary table, and pulverizing the raw materials by a pulverizing roller rolling on the rotary table. The present invention relates to a roller mill for generating fine powder, and more particularly to a technique for preventing self-excited vibration and improving the particle size of product fine powder.

[0002]

2. Description of the Related Art As one type of pulverizer for finely pulverizing agglomerates such as coal, cement raw material or new raw material, a vertical roller mill having a rotating rotary table and a plurality of rollers has been used. Is one of the representative models.

[0003] This type of crusher is a disk-shaped rotary table which is driven by a motor having a speed reducer at a lower portion in a cylindrical casing (housing) and rotates at a low speed on a horizontal plane. A plurality of crushing rollers which are rotated by being pressurized by a hydraulic pressure or a spring or the like at positions equally divided in the direction.

Chute (supply pipe) to center of rotary table
The crushed material supplied from the rotary table draws a spiral trajectory on the rotary table due to the centrifugal force caused by the rotation of the rotary table, moves to the outer peripheral portion, and crushes the groove-shaped crushing portion provided on the outer peripheral portion of the upper surface of the rotary table. It is caught between the rollers and crushed.

[0005] Hot air sent through the duct is guided to the base of the casing, and the hot air is blown upward from the air throat between the outer periphery of the rotary table and the inner wall of the casing toward the upper side of the mill. I have.

The powder produced by the pulverization is dried while rising in the casing by hot air blown from an air throat. The granules transported to the upper part of the casing fall from the coarse ones by gravity (primary classification), and the finer granules passing therethrough are re-classified by a rotary classifier provided at the upper part in the casing, and are subjected to predetermined classification. The fine powder having a particle size equal to or smaller than the particle size is conveyed by hot air, for example, in a boiler, to a pulverized coal burner or a fine powder storage bin.

[0007] Coarse particles larger than a predetermined particle size, which have not passed through the classifier, fall onto a rotary table and are again pulverized together with the raw materials just supplied into the mill. In this way, the crushing is repeated by the crushing roller in the mill.

[0008]

SUMMARY OF THE INVENTION In a coal-fired boiler,
Low-pollution combustion (low NOx and low unburned portion combustion) and wide-range load fluctuation operation have been performed. In order to realize low-pollution combustion, it is advisable to improve the particle size of the pulverized coal supplied to the boiler (the ratio of particles having a particle size smaller than a certain value). It has become required.

In order to improve the particle size of the granular material sent out from the roller mill, the number of revolutions of the rotary classifier should be increased.

As shown in FIG. 15, as the rotation speed of the rotary classifier is increased, the particle size of the granular material on the rotary table is improved. The pulverizing roller of the roller mill performs pulverization by a compressive force and a shearing force that bite the powder and granular material between the rotary table and the groove-shaped pulverizing part. At the same time, the weight of the pulverizing roller and the load for the pulverization are reduced. It is supported by layers.

When the particle size of the granular material is improved, the supporting force of the granular material layer becomes unstable, and as shown in FIG. 16, the granularity of the granular material and the particle size of the granular material layer between the rotary table and the grinding roller are increased. The thickness decreases. When the thickness becomes less than a certain value, self-excited vibration occurs. Since the self-excited vibration is so large as to make the operation of the roller mill impossible, the particle size of the granular material generated by the roller mill is practically determined by the conditions under which the self-excited vibration occurs.

An object of the present invention is to provide a roller mill which realizes stable operation without self-excited vibration over a wider range with respect to the number of revolutions of a rotary classifier, can produce fine powder of a good particle size, and has a high grinding efficiency. Is to do.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotary table which rotates around a vertical axis of a mill below a mill housing, a groove-shaped crushing section provided on an outer peripheral portion of the rotary table, and an upper surface thereof. In a roller mill having a plurality of crushing rollers that rotate to a position equally dividing the circumferential direction,
A first crushing portion on the inner circumference side and a second crushing portion on the outer circumference side are provided in the groove-shaped crushing portion on the rotary table, and the gap between the rotary table and the crushing roller is configured to be wider at the outer crushing portion than at the inner side. Achieved by a roller mill.

In the above means, the material to be crushed, which is a raw material, is supplied to the center of the rotary table from a chute (supply pipe), and is sent to the groove-shaped crushing section outside the rotary table by centrifugal force due to rotation of the rotary table. . The to-be-pulverized material mainly enters the inner peripheral side of the groove-shaped pulverizing portion divided into two portions, inner and outer, and reaches the outer peripheral side pulverizing portion after being pulverized once or several times by a pulverizing roller.

[0015] Therefore, the particle size is relatively poor (many particles having a large particle size) in the inner crushing portion, and the particle size is good (many particles having a small particle size) are good in the outer peripheral portion. In addition, since the gap between the rotary table and the crushing roller is narrowed in the crushing portion on the inner peripheral side, the surface pressure applied to the granular material is larger on the inner peripheral side.

Therefore, a large part of the crushing load of the crushing roller is supported by the crushing portion on the inner peripheral side where the stable granular material layer having a poor particle size is formed, so that the distance between the crushing roller and the rotary table is increased. The thickness of the granular material layer is kept thicker, and self-excited vibration hardly occurs.

[0017]

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

FIG. 1 shows an overall configuration of a roller mill according to an embodiment of the present invention as a vertical sectional view passing through the center axis of the mill.

In FIG. 1, a roller mill according to an embodiment of the present invention is driven by a motor (not shown) having a speed reducer in a housing 1 and rotates in a horizontal plane. A rotary table 3 having a concentric groove-shaped crushing portion 2, a crushing roller 4 disposed at a position dividing the circumference of the upper surface of the groove-shaped crushing portion into three equal parts, and a bracket 5 for fixing the crushing roller 4; A triangular pressure frame 6 for transmitting a load to the crushing roller 4, a pressure rod 7, a chute 9 for supplying a raw material 8 to the upper portion of the mill, and a rotary classifier 10.

The crushing roller 4 rotates in accordance with the rotation of the rotary table 3 around the shaft 11 fixed to the bracket 5 as a rotation axis. The bracket 5 is connected to the pressure frame 6 via a pivot 12 so as to have a degree of freedom of rotation about the pivot 12 as a rotation axis. The pressure rod 7 transmits a crushing load generated by a hydraulic pressure or a spring, and the crushing roller 4 is connected to the rotary table 3 via the pressing frame 6 or the like.
Press against

FIG. 2 is a perspective view showing the crushing roller 4 and the rotary table 3 in one embodiment of the present invention.

The material 13 to be crushed, which is a raw material, is supplied to the center portion of the turntable 3 and sent to the groove-shaped crushing section 2 on the circumference of the turntable 3 by centrifugal force generated by the rotation of the turntable 3. It is bitten between the crushing unit 2 and the crushing roller 4 and crushing is performed.

FIG. 3 is a partial sectional view showing a main part of an embodiment of the present invention. The groove-shaped crushing unit 2 of the rotary table 3 includes an inner peripheral side first crushing unit 21 and an outer peripheral side second crushing unit 22 both having an arc-shaped cross-sectional shape. Two arcs 4a, 4b as in
It has a cross-sectional shape of, and rotates around the shaft 11 as a rotation axis.

As shown in FIG. 4, the angle α between the horizontal line 25 and the tangent line 24 of the cross section of the first pulverizing section 21 at the connecting section 23 of the two pulverizing sections is defined by the tangent line 26 of the cross section of the second pulverizing section 22. And the angle β between the horizontal line 25 and the horizontal line 25.

Although the connecting portion 23 is shown at one point in FIG. 4, the connecting portion 23 may be a short curve. Considering the effects of processing and wear, it is more practical to use a short arc or straight line.

FIG. 5 is a partial cross-sectional view showing a state in which the material 13 to be ground is supplied to the groove-shaped grinding unit 2 and a powder layer 27 is formed between the rotary table 3 and the grinding roller 4. Things. The distance between the crushing roller 4 and the groove-shaped crushing section 2 is narrow at the first crushing section 21 on the inner peripheral side and wide at the second crushing section 22 on the outer peripheral side.

Therefore, the pressure applied to the granular material layer 27 is larger in the first pulverizing unit 21, and the load applied to the pulverizing roller 4 is mainly supported by the pulverulent material layer 27 in the first pulverizing unit 21.

FIG. 6 shows a state of pulverization in the groove-shaped pulverizing section 2.

The crushed object 13 is supplied from the center of the rotary table 3 and is carried to the on-groove crushing section 2 on the circumference of the rotary table 3 by centrifugal force generated by the rotation of the rotary table 3. Enter one crushing unit 21.

The object 13 to be crushed is divided into a first crushing section 21 and a second crushing section 21.
The powder is pulverized in the pulverizing section 22 and is conveyed to the rotary classifier 10 above the mill by hot air 28 blown from the outer edge of the turntable 3.

Since the raw material that has not been pulverized is first supplied to the first pulverizing unit 21 on the inner peripheral side, the particle size of the powder is adjusted to the first pulverizing unit 2.
1 is relatively coarse, and the second pulverizing section 22 is relatively fine.

That is, as compared with the conventional case where the particle size of the granular material is almost uniform in the groove-shaped crushing section 2, the first crushing section 21 mainly receiving the crushing load has a relatively coarse particle size. For this reason, the granular material layer 27 is kept thick, self-excited vibration is less likely to occur, and stable operation in a wider range can be realized.

On the other hand, from the point of view of the pulverizing action, the pulverizing action, which is pulverization by compressive force, works stronger as the surface pressure increases.
The grinding action, which is grinding by shearing force, works stronger as the peripheral speed difference between the rotary table 3 and the grinding roller 4 increases.

FIG. 7 shows the distance from the center of the rotary table 3 and the peripheral speed of rotation of the rotary table 3 and the crushing roller 4.

Since the peripheral speed is proportional to the distance from each rotary shaft, the difference between the peripheral speeds of the rotary table 3 and the crushing roller 4, that is, the relative speed is small in the first crushing section 21, and
Large in the crushing section 22.

Therefore, the grinding action, which is the grinding by the shearing force acting on the coal seam, is large in the second grinding section 22.

As described above, the roller mill of the present invention mainly performs the crushing action in the first crushing section 21 having a relatively coarse particle size, and mainly performs the crushing action in the second crushing section 22 having a relatively fine particle size. And realizes efficient pulverization.

FIG. 8 is a partial sectional view showing a main part of another embodiment of the present invention. The groove-shaped crushing section 2 of the turntable 3 includes an inner first crushing section 31 having an arc-shaped cross section and an outer second crushing section 32 having a linear cross section. Similarly, the cross-sectional shape of the rotary table 3 has a straight line on the outside and a circular arc on the inside.

By making the cross-sectional shape of the second crushing section 32 straight, the amount of the gap between the rotary table 3 and the crushing roller 4 can be made constant over a wider range than in the case of an arc-shaped cross-sectional shape. The grinding action can be performed in a wider range.

Also, as shown in FIG.
The angle α between the tangent line 34 of the cross section of the first crushing portion 31 and the horizontal line 25 in the connecting portions 33 of the first and second portions 32 is larger than the angle β formed by the cross section 35 of the second crushing portion 32 and the horizontal line 25.

However, in the cross-sectional shape of the groove-shaped crushing portion 2 shown in FIG. 8, since the slope of the outer edge portion 36 of the second crushing portion 32 where the crushed material 13 exits is gentle,
The powdery material at the outer peripheral portion that performs the grinding action is easily blown outward by centrifugal force, and it is difficult to form a sufficient powdery particle layer 27 in the second pulverizing section 32.

In order to prevent this, as shown in FIG. 10, a weir 37 is provided on the outer circumference of the groove-shaped crushing part 2 of the rotary table 3 to prevent the granular material from jumping out. In addition, the second pulverizing section 32 can hold a sufficient granular material layer 27.

FIGS. 11 (a) and 11 (b) are comparative explanatory diagrams showing the amount of the granular material depending on the presence or absence of a weir. When there is no weir as shown in FIG. 7A, the amount of the granular material layer 27 in the second pulverizing unit 32 is small, but when the weir 37 is provided as shown in FIG.
It turns out that the granular material layer 27 in the crushing part 32 increases.

FIG. 12 is a partial sectional view showing a main part of still another embodiment of the present invention.

The groove-shaped pulverizing section 2 is provided in two layers, inner and outer (41, 4).
2) The crushing roller 4 has a cross-sectional shape in which two arcs are connected so as to straddle both the two groove-shaped crushing portions 41 and 42. The gap between the crushing roller 4 and the rotary table 3 is narrowed by the inner groove-shaped crushing section 41 and widened by the outer groove-shaped crushing section 42, so that the inner groove-shaped crushing is relatively coarse and the coal seam is stable. The roller is supported by the portion 41, and self-excited vibration is less likely to occur.

Further, as shown in FIG.
The difference between the peripheral speed of the rotary table 3 and
1 is smaller at the outer groove-shaped crushing section 42 and larger at the outer groove-shaped crushing section 41, and is mainly crushed by the inner groove-shaped crushing section 41.
In this way, the grinding action mainly works, and the grinding can be performed efficiently.

FIG. 1 shows a roller mill of a type in which three rollers are supported and pressed by a triangular pressing frame common to them, but the shape of the pulverizing section shown in the present invention is a plurality of rollers. Can be applied to a roller mill of a type that independently supports and pressurizes.

FIG. 14 is a partial sectional view showing a main part of an embodiment of the present invention in a roller mill of a type which independently supports rollers.

The roller mill shown in this figure is driven by a motor (not shown) having a speed reducer, and rotates in a horizontal plane.
The rotary table includes a rotary table 3 having a groove-shaped crushing portion 2 concentric with the rotating shaft on the outer peripheral portion, and a crushing roller 4 disposed at a position equally dividing the circumference of the upper surface of the groove-shaped crushing portion 2.

The shaft 51 which is the rotation axis of the crushing roller 4
Are mounted on the housing 1 so as to be rotatable about a shaft 52, and each shaft 51 is
Can move independently of 1. The shaft 51 receives the force of pressing the roller against the groove-shaped crushing unit 2 by the hydraulic device 53, and crushes the raw material supplied on the table.

Also in the roller mill having the structure shown in FIG. 14, the first crushing portion 21 on the inner peripheral side and the second crushing portion 22 on the outer peripheral side are provided, and the gap between the roller and the table in the first crushing portion 21 is provided. And the gap in the second pulverizing section 22 is widened, whereby stable operation of the roller mill can be realized in a wide range of the classifier rotation speed.

[0052]

According to the present invention, in the pulverizing section of the roller mill, the granular material layer can be maintained in a more stable state. It is possible to realize a stable operation without any trouble and improve the particle size of the product fine powder.

[Brief description of the drawings]

FIG. 1 is a front view showing a partial cross section of the entire configuration of a roller mill according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a rotary table and a crushing roller of a roller mill according to an embodiment of the present invention.

FIG. 3 is a front view showing a main part of the embodiment of the present invention in a partial cross section.

FIG. 4 is a cross-sectional view showing a part of the groove-shaped pulverizing part according to one embodiment of the present invention.

FIG. 5 is an explanatory diagram showing surface pressure acting on a granular material layer in one embodiment of the present invention.

FIG. 6 is an explanatory view showing a state of pulverization of a powder or granular material in a groove-shaped pulverizing section.

FIG. 7 is an explanatory diagram showing a peripheral speed of rotation of a rotary table and a crushing roller according to an embodiment of the present invention.

FIG. 8 is a front view showing a main part of another embodiment of the present invention in a partial cross section.

FIG. 9 is a cross-sectional view showing a part of a groove-shaped pulverizing part according to another embodiment of the present invention.

FIG. 10 is a front view showing a modification of FIG. 8;

FIG. 11 is a comparative explanatory diagram showing an operation of another embodiment of the present invention.

FIG. 12 is a front view showing a main part of a further embodiment of the present invention in a partial cross section.

FIG. 13 is an explanatory view showing a peripheral speed of rotation of a rotary table and a crushing roller according to still another embodiment of the present invention.

FIG. 14 is a front view, partially in section, of a main part of an embodiment of the present invention in a roller mill of a type that independently supports rollers.

FIG. 15 is a characteristic diagram showing a relationship between the number of rotations of the rotary classifier and the particle size of the granular material on the rotary table.

FIG. 16 is a characteristic diagram showing the relationship between the particle size of the granular material and the thickness of the granular material layer.

[Explanation of symbols]

 Reference Signs List 1 housing 2 groove-shaped crushing section 3 rotary table 4 crushing roller 4a inner arc of crushing roller 4b outer arc of crushing roller 4 5 bracket 6 pressurizing frame 7 pressurizing rod 8 raw material 9 chute 10 rotary classifier 11 shaft 12 Pivot 13 Object to be crushed 21 First crushing part 22 Second crushing part 23 Connection part 24 Tangent line of cross section of first crushing part 21 Horizontal line 26 Tangent line of cross section of second crushing part 22 27 Granular material layer 28 Hot air 31 First Crushing part 32 second crushing part 33 connecting part 34 tangential line of the cross section of the first crushing part 35 cross section of the second crushing part 36 outer edge 37 dam 41 inner groove-shaped crushing part 42 outer groove-shaped crushing part 51 shaft 52 shaft 53 Hydraulic equipment

Claims (7)

[Claims] 1. A rotary table that rotates in a horizontal plane below a mill housing, a groove-shaped crushing section provided on the circumference of the rotary table, and a crushing roller that rolls on the groove-shaped crushing section in a pressurized state. Wherein the groove-shaped crushing portion includes a first crushing portion on the inner peripheral side and a second crushing portion on the outer peripheral side, and the cross section of the groove-shaped crushing portion is a vertical plane including a vertical line passing through the center of the rotary table. The angle α between the tangent of the cross section of the first crushing section and the horizontal line at the connection between the first crushing section and the second crushing section is the angle β between the tangent of the cross section of the second crushing section and the horizontal line at the connection section. Roller mill characterized by being large. 2. The roller mill according to claim 1, wherein the shape of the cross section of the vertical plane is a circular arc.
A roller mill comprising: a crushing unit; and a second crushing unit having a cross section formed by a vertical plane and having an arc having a larger radius than a cross section of the first crushing unit. 3. The roller mill according to claim 1, wherein the shape of the cross section of the vertical plane is a circular arc.
A roller mill comprising: a crushing unit; and a second crushing unit having a straight section in a vertical plane. 4. The roller mill according to claim 3, further comprising a weir on a circumference outside the groove-shaped pulverizing portion of the rotary table. 5. The roller mill according to claim 1, wherein a gap between the second crushing unit and the crushing roller is larger than a gap between the first crushing unit and the crushing roller. Roller mill characterized by the following. 6. A rotary table that rotates in a horizontal plane below the mill housing, and two groove-shaped crushing portions on a concentric circle of the rotary table, and is pressurized across both of the two groove-shaped crushing portions. A roller mill comprising a pulverizing roller that rolls with a roller. 7. The roller mill according to claim 6, wherein a gap wider than a gap between the inner circumferential groove-shaped crushing section and the crushing roller is provided between the outer circumferential groove-shaped crushing section and the crushing roller. A roller mill comprising: