JPH0389952A - Vertical mill - Google Patents

Abstract

PURPOSE:To reduce the operating power cost of a blower by providing a particle falling preventing plate in contact with the annular gap between the inner wall of a housing and an air jet passage and further setting the lower end of the air jet passage to the front in an advance direction at the time of the rotation of a grinding table. CONSTITUTION:A grinding part is constituted of the rotary grinding table 4 mounted to the lower part of a housing and the rollers 7 or balls pressing the solid substance supplied on the table 4 to the upper surface to the table 4. An air jet member 2 is mounted to the side edge part of the table 4 and an air jet passage 20 is formed to the member 2 to be inclined with respect to a horizontal surface. A particle falling preventing plate 22 is provided in contact with the annular gap between the inside wall of the housing and the passage 20 and, further, the lower end of the passage is set to the front in an advance direction at the time of the rotation of the table 4. As a result, the operating power cost of a blower sending air into a mill is reduced and the service life of a throat ring can be extended.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pulverizing device for pulverizing, drying and classifying coal, cement raw materials, etc., and particularly relates to a vertical mill suitable for reducing operating power and maintenance costs. .

[Prior Art] Vertical roller mills are used, for example, in pulverized coal manufacturing equipment for coal-fired boilers that use pulverized coal as fuel.

A conventional vertical roller mill will be explained with reference to FIGS. 9 and 10. A disc-shaped grinding table 4 is arranged at the bottom of the vertical roller mill, and this grinding table 4 is connected to a gear box 5. The crushing table 4 is configured to rotate at 20 to 40 rpm via a gear (not shown) in a gear box 5 that is rotationally driven by a motor 61.

An annular crushing ring 6 having a concave top surface is fixed on the outer periphery of the top surface of the crushing table 4 . A plurality of crushing rollers 7 are pressed against the upper surface of the crushing ring 6 by an upper pressure frame 8, and rotational force is applied by the crushing ring 6 through the object to be crushed.

The pressure applied to the pressure frame 8 is adjusted by a pressure cylinder 11 via a spring 9 and a spring frame 10. Grinding table 4. The crushing ring 6 and the crushing roller 7 constitute a crushing section. A material to be crushed, such as coal, is introduced between a crushing ring 6 and a crushing roller 7, and is crushed and crushed into powder. A coal feeding pipe 3 is provided above the center of the pulverizing section, and the pulverized powder and granules around this pipe are sorted according to their size, those below a predetermined particle size are transferred to a burner, and those that do not reach a predetermined particle size are transferred to the burner. A classifier 13 is provided for return to the crushing section. A coal feed pipe 17 is provided above the classifier 13 to transport the fine particles to the burner of the boiler.

The crushing section and the classifier 13 are housed in the cylindrical housing 1, and the space between the inner wall of the housing 1 and the outer peripheral surface of the crushing section and the classifier 13 is used to transport the crushed powder and granules by air. It forms a flow path where the flow is carried out. The air for transfer is passed through a throat ring 12 which is an annular air jet flow path formed by the outer periphery of the crushing table 4 and the inner wall of the housing 1.
It is becoming more supplied.

The throat ring 12 is usually divided into 30 to 50 equal parts by throat vanes 20, as shown in FIG. Further, the throat vane 20 is attached to the housing side in an inclined state relative to the horizontal plane.

Next, the operation of the above-mentioned vertical roller mill will be explained using FIG. 11.

5-2 supplied onto the crushing table 4 through the coal feed pipe 3
Coal of approximately 0 mm is pulverized into pulverized coal while passing through the gap between the pulverizing ring 6 and the pulverizing roller 7 due to the centrifugal force generated by the rotation of the pulverizing table 4.
The transfer air A is blown upward to the throat upper part 12a, which is the upper part of the table, while rotating slightly in the direction of rotation of the table. Coarse particles among the coal particles blown upward are separated from the airflow and returned onto the grinding table 4 (-second classification).

In addition, particles with a small particle size are removed from the housing along with the air.
rise along the line and pass through the classifier Höhn]4 to the classifier 13
Flow inside.

A swirling flow of air accompanied by pulverized particles is generated inside the classifier 3, and the particles are subjected to centrifugal force and descend while swirling on the inner wall of the classifier 13, passing through the flapper 15 to the pulverizing table 4.
It falls upwards and is re-shattered.

On the other hand, fine particles that are only subjected to a small centrifugal force are not separated and are discharged out of the system along with the air (secondary classification).

The coal thus supplied into the vertical roller mill is circulated within the mill several times until it reaches a predetermined particle size, and then is taken out of the system as a product. The amount of coal circulating in the mill, i.e. the grinding table4. Grinding ring 6 and grinding roller 7
The amount of coal that passes through the pulverizing section, which is comprised of three or more components, varies depending on the particle size of the product, but is 5 to 10 times the amount of the product, and about half of it is returned in the primary classification.

In addition, the flow velocity of the air passing through the throat ring 12 is normally 10 k
In order to keep the speed below g/h, it is usually operated at a high speed of around 50 m/s.

In Fig. 11, 51 to 55 indicate pressure outlet ports, and the total pressure loss ΔP of the mill expressed by the pressure difference between the air supply port 2 and the mill outlet 18 is as follows: Air A passes through the throat ring 2 at high speed. Throat differential pressure ΔP1 generated at this time and throat upper part 12
Coal seam differential pressure ΔP2, which is the pressure loss caused by the fluidized bed of particles transported in a suspended state in a, and conveyance differential pressure ΔP, which occurs when the fine particles classified by -order are transported to the classifier 13 by airflow. , and the pressure loss ΔP4 of the classifier 13 (see FIG. 11). Among these, the throat differential pressure ΔP2 accounts for about 60% of the total. Upper throat 1
Since the fluidized bed 2a rises while rotating weakly in the same direction as the rotation of the table, the fluidized bed has uneven flow of particles and a stagnation part where the particles are high in density. Therefore, the pressure loss in the fluidized bed section, that is, the differential pressure in the coal bed ΔP2 is dominated by the pressure loss in the stagnation section, and becomes an extremely large value compared to the pressure loss in the high-speed fluidized bed.

In order to reduce the throat differential pressure, an apparatus has been proposed in which the throat vane 12 is attached to the side edge of the grinding table instead of being attached to the housing side. In addition, as this type of device, for example, Japanese Patent Application Laid-Open No.
Publication No. 64645.

Utility Model Application No. 62-144548, Utility Model Application No. 621519
For example, Publication No. 48 may be mentioned.

[Problem to be solved by the invention]

In the conventional vertical roller roller, in which the throw 1 is attached to the housing side, the air A passing through the throat ring 12 is maintained at high speed.
This prevents particles from falling from 2. This causes an imbalance in the air flow velocity (hereinafter referred to as the throat flow velocity) passing through each throat (the air injection passage where the throat ring is partitioned by the throat vane is referred to as the throat), and in particular, This is because the throat flow velocity is low at the throat located next to the part where the particles are caught in the crushing roller ruff, and the throat flow velocity fluctuates rapidly, so the particles are falling more intensively than the throat in this area. be. Therefore, although a throat flow velocity of several m/s is theoretically sufficient to prevent particles from falling, it is normally operated at a high speed of around 50 m/s.

Due to this high flow rate, the throat differential pressure ΔP is also larger than necessary. Furthermore, the local friction of the throat portion, which is the air injection material, is severe, and the life span of the throat ring, etc., is short, resulting in an increase in maintenance costs due to replacement of the throat ring, etc.

On the other hand, in a vertical roller mill in which an air injection member is attached to the side edge of the grinding table, as in the example shown in JP-A-60-064645, the amount of particles falling from the throat can be reduced, but the throat flow velocity is If the operation is performed at a speed significantly lower than before, a large amount of particles will fall through the gap between the housing and the throat vane, so it is necessary to maintain the throat flow rate at a flow rate slightly lower than before. Therefore, the throat differential pressure reduction effect is small. However, in this case, local wear of the throat is eliminated, and the life of the throat can be extended.

Conventional vertical roller mills have a problem in that in order to maintain a high throat flow rate, a large pressure loss occurs in the throat ring, which increases the operating power cost of a blower that sends air A to be supplied into the mill.

Furthermore, the throat ring is subject to severe wear, which shortens the life of the throat ring, requires frequent replacement of the throat ring, and increases maintenance costs.

An object of the present invention is to solve the problems of the prior art described above, and to reduce the throat flow velocity, reduce the throat differential pressure ΔP1, and further reduce the coal seam differential pressure ΔP2, thereby sending air into the noble coal. It is an object of the present invention to provide a vertical mill capable of reducing the operating power cost of a blower and extending the life of a throat ring.

[Means to solve the problem]

The object is to provide a grinding table having an upright cylindrical housing, a grinding ring that rotates horizontally at its bottom and has a concave top surface, a grinding roller or grinding pole that rolls on the grinding ring, and a grinding table having a grinding roller or a grinding pole that rolls on the grinding ring, and a grinding table that has a grinding ring that rotates horizontally at its bottom and has a concave upper surface, and In a vertical roller mill in which an air injection passage is formed by attaching multiple throat vanes inclined at By configuring the vane so that the lower end of the vane is at the front in the direction of movement when the crushing table is rotated, the vane can be moved further.

[Effect]

In the vertical roller mill of the present invention, the annular gap between the inner wall of the housing and the throat vane serving as the air injection member is closed by a fall prevention plate. therefore,
Even if the particles sent to the throat from the crushing section collide with the inner wall of the housing, they will not fall through the annular gap between the inner wall of the housing and the throat vane, significantly reducing the flow velocity at the throat. Be able to drive.

Furthermore, by injecting air from the throat in the opposite direction to the rotation direction of the table, the fluidized bed above the throat is also significantly reduced, making it possible to operate with significantly reduced resistance in the fluidized bed section.

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

1 to 6 show embodiments of the present invention. The present invention relates to an improvement of the air injection passage, and other parts are the same as those of the conventional vertical roller mill. Therefore, since the main parts of the vertical roller mill other than the improved parts have already been explained, their explanation will be omitted.

FIG. 1 is a longitudinal sectional view of an air passage portion of a vertical roller shaft according to the present invention. In this figure, the same parts as in the conventional example shown in FIG. 9 are given the same reference numerals. As shown in FIGS. 1 and 3, a plurality of throat vanes 20 as air injection members are attached to the side edge of the crushing table 4,
A particle fall prevention plate 22 with a rectangular cross section is provided along the annular shape in contact with the annular gap between the throat vane 20 and the annular ledge cover 21 with a triangular cross section attached to the inner wall of the housing. . Note that it is desirable that the throat vane 20 has a streamlined shape in its gas population portion (lower end portion) from the viewpoint of reducing differential pressure and reducing the amount of falling coal.

Furthermore, the rotation direction of the table, that is, the grinding table] 1 The throat vane 20 attached to one pull 4 is configured such that its lower end is at the front in the traveling direction when the grinding table 4 rotates, and therefore the throat vane 20 is The direction of rotation is such as to suppress air intake, as shown in FIG.

Next, the operation will be explained.

Air A from the air supply port 2 is introduced through a throat partitioned by a throat vane 20 rotating in the same direction as the grinding table 4. In a conventional vertical roller mill that uses a fixed throat, the particles that are sent from the crushing section to the throat are transported to the throat near the roller throat where more particles are transported than to other throats. As a result, particles tend to fall from the throat near the biting part. For this reason, in order to prevent the particles from falling, a flow velocity higher than necessary is given in the throat to increase the throat differential pressure ΔP, which is the opening.

Furthermore, as shown in Figure 7, simply attaching the throat vane to the side edge of the crushing table (B) reduces the amount of coal falling from the throat compared to the conventional fixed throw (C). , a large amount of particles fell through the annular gap between the inner wall of the housing and the throat vane.
In the end, it is necessary to maintain the throat flow rate at a slightly lower flow rate than before. Note that if the gap between the table and the hone is set to 5% or less with respect to the width of the throat ring 12, the amount of coal falling from the throat can be suppressed as in the case where a particle fall prevention plate is attached.

The present invention has been made in view of this point, and the particle fall prevention plate 22 is installed in contact with the upper side of the annular gap between the inner wall side of the housing and the throw 1 heben 2o, and has a length that is approximately the same as the gap. By providing this, it is possible to prevent particles from falling as shown by A in Figure 7, and by increasing the opening area of the throat, it is possible to operate at a much lower throat flow velocity than before, and the throat differential pressure can be reduced. Not only can ΔP1 be reduced, but by lowering the throat flow velocity, the occurrence of wear on the throat portion (air injection member) can be further reduced, and the amount of wear can also be significantly reduced.

Furthermore, in the present invention, when the grinding table 4 rotates, the
The lower end of the hebane 20 is configured to be at the front in the traveling direction. In this embodiment, when viewed from above the crushing table 4, the rotation direction is counterclockwise. Therefore, air is injected from the throat in the opposite direction to the rotation direction of the table, and the particles that are given a counterclockwise rotation by the rotation of the crushing table and sent to the throat upper part 12a are rotated clockwise by the air from the throat. The particles are given kinetic energy and rise directly above the fluidized bed portion of the throat upper portion 12a with substantially uniform particle density. At this time, the stagnation that existed in conventional fixed throats is significantly reduced.

In other words, the density of the fluidized bed portion becomes smaller. Therefore, the resistance of the fluidized bed portion is greatly reduced, and the coal bed differential pressure ΔP2 can be significantly reduced. An example of the results is shown in FIG. FIG. 8 shows a comparison between the conventional fixed throat (C) and the rotating throat (A) according to the present invention with respect to the coal seam differential pressure ΔP2.

Figure 8 shows the relationship between the coal seam differential pressure ΔP2/ΔPz'' and the amount of coal in the mill, that is, the hold amplifier W/W. I understand.

It should be noted that when the rotary throat is rotated in the opposite direction to the present invention, that is, in the case of clockwise rotation (B), the differential pressure in the coal seam is reduced compared to the conventional fixed type, but it can be seen that the reduction effect is small.

The rotation speed of the throat vane 20, that is, the crushing table 4
The rotation speed of a practical machine is around 30 rpm, and compared to general rotating machines such as blowers, the rotation speed is ]/10
It is as follows. Further, the throat differential pressure in the rotary throat also varies depending on the rotation direction and rotation speed. That is, in the case of reverse rotation, the throat differential pressure is about 10 to 20% larger than that in normal rotation, and this tendency becomes more noticeable as the rotation speed increases or decreases. This means that in the case of reverse rotation, the flow velocity in the throat is the flow velocity in the throat of a fixed throat with the throat rotation speed component added, and in the case of forward rotation, the flow velocity in the throat is reduced by the rotation speed component. considered to be a thing.

[Other embodiments of the invention]

5 FIGS. 4 to 6 each show other embodiments of the present invention. Fourth
In the figure, the throat hone 20 has a structure in which the upper end surface and the lower end surface are each inclined upward in the radial direction of the crushed chiffle 4 with respect to the horizontal plane, and the throat hone 20 side of the ledge cover 21 having a triangular cross section A particle fall prevention plate 22 having a rectangular cross section is provided along an annular shape at the tip.

In FIG. 5, a protrusion covering a part of the upper end surface of the ledge cover 21 is formed at the upper end of the throat hone 20, which has an inclined structure similar to FIG. -21, a particle fall prevention plate 22 having a rectangular cross section is provided along an annular shape.

In FIG. 6, the upper and lower end surfaces of the throat hone 20 are located in the horizontal direction, and the ledge cover 2
A concave portion is formed in an annular shape on the throat moon 20 side,
A bent piece provided at the upper end of the throat vane 20 is disposed in this recess, and a particle fall prevention plate 22 having a rectangular cross section is provided along an annular shape on the upper surface of this bent piece.

Also in the case of FIGS. 4 to 6, the lower end of each throat vane 20 as an air injection member is configured to be at the front in the advancing direction when the crushing table 4 rotates.

In the above-mentioned embodiments, a vertical mill having a crushing roller was explained as an example, but it goes without saying that the present invention can also be applied to a vertical mill having a crushing ball.

〔Effect of the invention〕

According to the present invention, since the amount of coal falling from the throat can be reduced, it is possible to operate at a throat flow velocity that is much lower than that of the conventional method. For example, according to one embodiment of the present invention, even if the throat flow velocity is reduced by 20%, the amount of coal falling is reduced to 10 kg.
/h or less, and the throat differential pressure was reduced by more than 73 points compared to the conventional model. Furthermore, by lowering the throat flow velocity, the amount of wear on the throat portion can be significantly reduced.

Furthermore, since the stagnation area in the fluidized bed section above the throat is eliminated, the differential pressure in the coal bed can be reduced by more than 1/3 compared to the conventional method. Therefore, the operating power cost of the transportation air blower can be significantly reduced compared to the conventional method, and the maintenance cost for replacing the throat portion can also be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the air injection passage of the vertical roller mill of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the orientation of the throat hone as an air injection member and the rotation direction of the table.
Figures 3, 4, 5, and 6 are partially enlarged views of the air injection passage shown in Figure 1, and Figure 7 shows the effect of reducing the amount of coal falling from the throat in an embodiment of the present invention. FIG. 8 is an explanatory diagram showing the effect of reducing differential pressure in the coal bed in an embodiment of the present invention. FIG. 9 is a schematic diagram of a conventional vertical roller mill. FIG. 10 is a partially cutaway diagram of FIG. 9. Cross-sectional view shown in 1st
FIG. 1 is an explanatory diagram of the total pressure loss inside the tip, showing a partially enlarged view of the vertical roller mill shown in FIG. 9. 1...Housing, 2...Air supply port, 3...Coal feed pipe, 4...Crushing table, 5...Gear box, 6... Grinding ring, 7... Grinding roller, 8... 8... Pressure frame, 9... Spring, ]O
... Spring frame, 11 ... Pressure cylinder, 12 ... Throat ring, 12a
...Top of throat, 13...Classifier,
14... Classifier vane, 15... Flapper, 16... Classifier inner cylinder, 17...
Coal transport t, 1B...5 exit, 20...
Throat vane, 21...Ledge cover 22
... Particle fall prevention plate, 61 ... Motor, A ... Air, B ... Coal.

Claims (1)

[Claims] (1) A crushing section consisting of a rotating crushing table provided at the bottom of the housing, rollers or balls that press the solid material supplied onto the crushing table against the top surface of the crushing table, and a side edge of the crushing table. In the case where an air injection member is attached, an air injection passage is formed for the air injection member, and the air injection passage is inclined with respect to a horizontal plane, an annular gap between the inner wall of the housing and the air injection passage is provided. A vertical mill characterized in that a particle fall prevention plate is provided in contact with the air injection member, and the lower end of the air injection member is positioned forward in the direction of movement when the grinding table is rotated.