JPH04371240A - Roller arm spindle device for roller mill - Google Patents

Abstract

PURPOSE:To provide the roller arm spindle device for the roller mill capable of being applied under a widely ranging load and to many kinds of coal by preventing the synchronized oscillation and vertical vibration of a crushing roller. CONSTITUTION:The distance between the center axis of a crushing roller in its cross section and a supporting shaft, i.e., the length of the oscillating region, is differentiated for each crushing roller.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a roller mill that uses a rotating table and a grinding roller to finely grind solid fuel such as coal, limestone, cement clinker, or solid raw materials for various chemical products. This invention relates to a roller arm spindle device that prevents the generation of vibration and noise under low load operating conditions in a roller mill that is independently supported and pressurized like a burr.

0002

[Conventional technology] Coal-fired boilers use low-pollution combustion (low NO
x, reduction of unburned content in ash) and wide-area load operation, and accordingly, the performance of pulverizers (mills) is also required to be improved. Vertical roller mills that use a rotating table and multiple rollers have become widely used as a type of mill for finely pulverizing lumps such as coal, raw materials for cement, or raw materials for new materials. It is solidifying its position as one of the models.

[0003] This type of mill has a roughly disk-shaped grinding table that is located at the bottom of a cylindrical housing and is driven by an electric motor and rotates at low speed via a reduction gear, and a grinding table that is located on the upper surface of the outer periphery of the table. It is equipped with a plurality of crushing rollers that are rotated by being pressurized by hydraulic pressure or a spring at positions equally divided in the circumferential direction. The raw material to be crushed is supplied from the chute to the center of the table, moves to the outer periphery of the table by drawing a spiral trajectory due to centrifugal force on the table, and is caught between the crushing race surface of the table and the crushing roller. Shattered.

Hot air is directed through a duct into the lower part of the mill housing and blows up from an air throat between the table and the housing. The powder after pulverization is dried while rising inside the housing by hot air blown from the air throat. The powder and granules transported above the housing fall down by gravity (primary classification) and are re-pulverized in the crushing section.

[0005] The slightly fine powder that has passed through this primary classification section is classified again by a cyclone separator or rotary separator (rotary classifier) provided at the upper part of the housing. Fine powder smaller than a predetermined powder diameter is conveyed by airflow and sent to a pulverized coal burner or a fine powder storage bin in the boiler. Coarse particles with a predetermined particle size or more that have not passed through the classifier fall onto the table and are crushed again together with the raw material (lump coal) that has just been fed into the mill. In this way, pulverization is repeated within the mill to produce fine product powder.

[0006]

Problem to be Solved by the Invention When attempting to operate a roller mill at a low load, vibration of the mill becomes a problem in reducing the load. This vibration phenomenon is complex and the detailed mechanism has not been clarified, but it is a type of frictional vibration caused by the slippage between the coal seam and the roller.
This is considered to be a stick-slip motion known as a typical example of discontinuous nonlinear vibration. As a type of vibration, it can be considered as a type of self-excited vibration because the source of the vibration cannot be clearly identified and the displacement waveform of the vibration has a sharp spike shape.

[0007] With ordinary coal, as shown in Figure 14, this vibration becomes intense during low-load operation (conditions with little hold-up in the mill), but depending on the type of coal, this vibration occurs even during considerably high-load operation. This may occur. The grindability of coal that tends to cause such vibrations varies from good to quite poor. Therefore, it is generally difficult to predict in advance whether coal is likely to cause vibrations based solely on its pulverizability.

FIG. 15 is a sectional view showing the support structure of the crushing roller during vibration. In this type of roller mill, individual grinding rollers 1301 are held like cantilevers on roller arms 1302. By restraining the downward movement of the roller arm 1302, the stopper device 1315 and the stopper seat 1316 prevent the grinding surface of the grinding roller 1301 and the grinding ring 131 from moving downward.
A setting gap δ is provided between the grinding races 1316 corresponding to the upper surfaces of the grinding wheels 5.

This gap δ is provided to prevent the crushing roller 1301 and the crushing race 1306 from coming into contact with metal during idle rotation when there is no coal. A roller mill in which this type of pressure support structure is applied to the grinding roller has a problem in that the pressurizing and holding devices of the grinding roller, including the roller arm 1302, are easily damaged by metal touch rotation.

Generally, during high-load crushing, the crushing roller 13
01 bites a large amount of raw material, and a thick compressed powder layer 1309 is created under the crushing roller 1301.
01 lifts up the roller rotation shaft 1303 as the rotation shaft. In this state, the crushing roller 1301 rotates stably without shaking its head and crushes the raw material.

FIG. 13(a) shows the vibration displacement of the roller during normal crushing. It can be seen that the rollers rotate extremely stably with almost no vibration. When the crushing roller 1301 actively bites the raw material, such as at startup when coal feeding begins or when the load increases, the crushing roller 1301 swings around the roller rotation shaft 1303, but in this swinging motion, the The movements of the individual crushing rollers are not synchronized (they do not move in the same phase). At this time, the mill begins to vibrate, but since the movements of the other grinding rollers are not synchronized, the vibration becomes a broad forced vibration whose dominant frequency cannot be determined, and the operation of the mill is not hindered.

On the other hand, when coal, which is particularly prone to vibration, is crushed under low load conditions, the thickness of the powder layer caught by the crushing roller 1301 and the initial setting gap δ are approximately the same, as shown in FIG. The rotation of the crushing roller 1301 becomes extremely unstable. In other words, when the grinding roller 1301 and the powder layer are in strong contact, a frictional force acts on the grinding roller 1301, but when the powder layer 1309 becomes thin, no resistance acts on the grinding roller and it rotates only due to inertia, so-called frictional vibration. (stuck-slip motion).

FIG. 13(b) shows the fluctuation of the vibration displacement of the roller during this vibration. The waveform is a spike-like non-sinusoidal wave, suggesting that strong acceleration occurs during vibration. When one crushing roller begins to make such a pendulum-like movement (α) in the vertical direction, the vibrations cause the crushing roller 901 → crushing roller support device →
Housing 902 → Grinding roller 903 (or 904
). In a mill having a structure in which a roller support device is fixed to a housing, an impact is transmitted to the housing, which is a thin cylindrical grain, and there is a risk that the housing may be damaged.

On the other hand, in order to protect the housing, FIG.
2, the vibrations generated by the crushing roller 1001 are directly transmitted from the rotary table 1007 (100
a) or rotary table 1007 → reducer 1008
→ It propagates to other crushing rollers along the path (100b) of the basement 1006, or through the path (100c) of the roller arm 1003 → spindle 1004 → roller support base 1005 → basement 1006.

[0015] From the above, in order to suppress the vibration of the mill by devising the hardware of the crushing section, it is important that the three crushing rollers move synchronously, that is, to prevent in-phase movement. I understand that there is something.

Based on the above-mentioned idea, the object of the present invention is to prevent the crushing rollers from shaking their heads in synchronization or vibrating up and down, and to prevent the crushing rollers from shaking their heads in synchronization or vibrating up and down, and to handle a wide range of loads or multiple types of coal without causing vibration. An object of the present invention is to provide a roller arm support device for a roller mill that enables operation of the roller mill.

[0017]

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following means. The distance between the roller cross-sectional center axis and the roller arm support shaft, that is, the length of the pendulum movement of the roller, is changed for each roller. In this case, the length of the pendulum movement of the rollers is changed by changing the arm length of each roller and the size of the spindle support base that fixes the spindle to the housing. Even if the arm length of each roller changes, the initial setting load (pressure device base) for each roller is adjusted so that the effective crushing load of each roller is equal.

[0018]

[Operation] By changing the length of the pendulum motion of each roller, the vertical amplitude and frequency of each roller that is about to vibrate will differ. That is, the longer the pendulum arm, the greater the amplitude but the lower the frequency. On the other hand, if the arm of the pendulum motion is shortened, the amplitude will be small and the frequency will be high. As a result of the above-described action, the vibrations of the rollers become random, and it becomes possible to prevent the rollers from oscillating in the same phase (synchronized).

[0019] By canceling the movements of the rollers in this way, even if the mill has to be operated in the vibration generation area as shown in Fig. 14, even if the vibration is about to occur, it will be reduced to a weak forced vibration. is suppressed. Therefore, it becomes possible to prevent the development of violent self-excited motion that could lead to damage to the equipment.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized by the structure of the spindle device in the roller arm of the grinding roller, so this will be explained first, and the overall structure of the mill will be explained later.

FIG. 2 shows the support structure of the crushing roller. The crushing roller 201 has a roller arm 20 with a shaft inside.
2 is supported like a cantilever. roller arm 20
On the base side of 2, there is a pressure lever 2 that protrudes upward.
03 is provided, and a crushing load is applied from a pressurizing device 204 so as to push this pressurizing lever 203 forward. A support shaft 20 is provided at the bottom of the base side of the roller arm 202.
6, and this support shaft 206 is supported by a support shaft holder 207 fixed to the housing 205.

Further, a protruding stopper 208 is provided at the bottom of the roller arm portion. Grinding roller 201
In order to prevent the crushing race 213 from touching the metal, the crushing roller 2 is
01 is configured such that this stopper 208 hits the stopper receiving seat 209 if it falls too far.

In a roller with such a cantilever type support structure, the oscillation length (or span of pendulum-like movement) L is the center of the cross section of the support shaft 206 and the crushing roller 201, as shown in FIG. Defined by the distance of axis 218 (parallel to roller rotation axis 217).

A feature of the present invention is that the oscillation length L is changed for each crushing roller. L1 in Figure 2
is an intermediate (standard) grinding roller among the three grinding rollers in the same mill. The oscillation length L2 of the crushing roller in Figure 3 is the shortest among the three crushing rollers, and L2 in Figure 4 is the shortest among the three crushing rollers.
3 is the longest.

In the embodiment of the present invention, the oscillation length L is varied by changing the length of the roller arm of each crushing roller. The maximum deviation of the swing length L between each crushing roller is set to 30%. If there is not much difference in L (
(for example, less than 3%), the difference in L is canceled out by the variation in the thickness of the compacted powder layer under the roller. On the other hand, a structure in which L is too long is not only dimensionally impossible because the distance between the crushing roller and the housing is limited, but also may cause significant unbalanced vibration.

Furthermore, when the length of the roller arm is changed to make L different, even if the set pressure in the pressure device (204 in FIG. 2) is the same, the so-called lever principle with the support shaft 206 as the fulcrum is applied. The crushing roller compresses the powder layer 216
The effective crushing load applied to the grinding roller differs depending on the crushing roller. Therefore, taking into account the deviation in the length of the roller arm,
Adjust the initial setting pressure in the pressurizing device.

Next, the overall configuration of a roller mill equipped with a roller arm support device for a crushing roller will be explained based on FIG. 1. 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 falls onto a rotary table 3 rotating at the lower part of the mill. Centrifugal force acts on the raw material to be crushed on the rotary table 3, and the raw material to be crushed is fed onto the crushing ring 13 on the outer periphery of the rotary table 3.
A crushing race 14 having a substantially arc-shaped cross section is carved on the upper surface of 3.
At the top, the powder is compressed and pulverized by a pulverizing roller 4.

The pulverized powder is blown into the mill through hot air 17 that passes between the throat vanes 18.
It is transported to the upper part of the mill while being dried. Fairly coarse particles fall onto the rotary table 3 due to gravity and are re-pulverized in the crushing section (primary classification). The particle group passing through this primary classification section is centrifugally classified by the rotary classifier 20 (secondary classification). Relatively coarse particles are blown to the inner wall of the housing 11 by centrifugal force, fall by gravity, and are re-ground. The fine particles penetrate between the blades of the rotary classifier 20,
The product is discharged from the product fine powder discharge duct 22 as product fine powder. In the case of coal, it is either sent directly to a pulverized coal burner (hot air 17 becomes the primary air for combustion) or collected into a storage bin.

FIG. 5 shows a comparison between (a) the results of the embodiment of the present invention and (b) the results of the prior art regarding the frequency distribution of acceleration measured in the reduction gear (gearbox) at the bottom of the rotary table. In the frequency distribution in the embodiment of the present invention shown in (a), there are no dominant frequencies, the peaks are low, and the shape is extremely broad.

From this characteristic as well, it is clear that the crushing section of the roller mill embodying the present invention does not undergo self-excited vibration. This is thought to be due to the effect of varying the swing length of the roller arm for each grinding roller in order to vary the amplitude and frequency of the pendulum-like motion of each grinding roller in the same mill. Since the movements of the crushing rollers are not synchronized, the pendulum-like movements that cancel each other out become random, and it is predicted that this results in slight irregular vibrations, that is, forced vibrations.

As shown in (b), it can be seen that in the case of the prior art, there is a dominant frequency with a high peak. Because the vibration waveform is distorted, dominant frequencies with gradually lower peaks appear, like harmonics. The fact that the speed reducer vibrates regularly at a specific frequency in this way indicates that the crushing roller is violently self-excited to vibrate in the same phase.

FIG. 6 is a schematic diagram showing the vibration of the crushing roller 501 when the swing length L is increased. When L is long, the amplitude of the vertical vibration of the crushing roller 501 on the compressed powder layer 508 is the same as that of the roller arm 502.
This is partly because L is long, so it is relatively large (compared to the case where L is short, as will be described later), and the vibration frequency is small. That is, the crushing roller 501 vibrates at a low frequency and with a large amplitude.

FIG. 7 shows the crushing roller 5, contrary to the example shown in FIG.
Grinding roller 51 when the swing length L of 10 is short
It depicts the movement of 0. In this case, the crushing roller 5
The amplitude of the vertical vibration of No. 10 is lower than that of the example of FIG. 6, and the frequency of the vibration is high.

FIG. 8 summarizes the changes in amplitude with respect to coal hold-up in the mill, and compares the characteristics of the embodiment of the present invention (FIGS. 1 to 4) and the conventional technology without countermeasures (FIG. 15). The amplitude δ0 C * on the vertical axis is made dimensionless by dividing by the amplitude δ0 C * at the rated load (W/W*≦1). On the other hand, the hold up W on the horizontal axis is made dimensionless by dividing by the hold up W* when the mill is operated at the rated coal feed amount (rated load).

This experimental result was obtained when coal, which is prone to vibration, was pulverized. In the case of no measures,
While the amplitude was significantly large in the low load band (W/W*≦0.25), in the case of this example, a significant reduction in the amplitude was confirmed. Even in the case of this example, W/W* ≦
At 0.25, the amplitude is slightly larger than when the load is high, but as mentioned above, this is considered to be one type of forced vibration.

FIG. 9 shows the change in product fine powder particle size with respect to the amount of coal fed. The particle size q on the vertical axis is the rated coal feed Q
Standard fine particle size q* in conventional mill when C*
It is divided by and expressed as a relative value. The amount of coal fed Q on the horizontal axis is also made dimensionless by dividing by QC*. The amount of coal fed QC on the horizontal axis is also made dimensionless by dividing by QC*. Generally, as QC/QC* decreases, the particle size of the product fine powder becomes finer and q/q* increases. However, in a cantilever type roller mill such as the one targeted by the present invention, in order to float the grinding roller from the grinding race (
The stopper (to prevent metal touch) is activated, and the q/q
* tends to decrease after reaching a peak when Q/Q*≦0.4.

[0037] In the examples of the present invention, it was found that the particle size of the product fines was almost the same as compared to the prior art. In other words, it can be seen that the improvement of the crushing roller support shaft (with respect to vibration suppression) to the extent embodied in the present invention does not result in a large difference in the crushing performance.

FIG. 10 shows a comparison of the amount of wear of grinding rollers with different roller arm lengths after long-term use. Although the amount of wear is expressed as a relative value, the difference is only within a few percent, and it is difficult to think that the difference is significant due to changing the length of the roller arm. Therefore, it can be seen that even if the oscillation lengths of the grinding rollers are made different as in the present invention, abnormal grinding that causes a large difference in the amount of wear between the grinding rollers does not occur.

The roller mill equipped with the roller arm spindle device of this embodiment is not limited to the mill for the coal-fired boiler described as an example, but can also be used for 1) a mill for oil coke, which is the same fixed fuel, 2) limestone for desulfurization. 3) A mill that pulverizes steel slag and non-ferrous smelting slag 4) A cement finishing mill that pulverizes cement clinker 5) A mill that pulverizes raw materials for various chemical products as well. can do.

[0040]

Effects of the Invention According to the roller arm support shaft device for a roller mill according to the present invention, the following effects can be achieved. (1) Mill vibrations caused by roller slippage can be prevented. This improves the durability of various equipment, including the mill itself. Additionally, the reliability of the entire thermal power plant increases. (2) Low-load operation becomes possible, and the minimum load on the mill can be further reduced. This expands the operating range of the boiler. Since it becomes possible to burn coal exclusively in the low-load operation range, the consumption of auxiliary fuel oil can be reduced. Therefore, the entire thermal power plant can be operated more economically. (3) Coal whose particles tend to break flat and cause more violent vibrations, coal which tends to adhere to rollers and races,
Alternatively, even with coal, which has a high calorific value per unit weight and tends to require low-load operation of the mill, it is possible to operate it without causing vibration. In this way, the range of coals applicable to thermal power plants is significantly expanded. (4) Vibration can also be suppressed by controlling the pressure and the rotational speed of the table or rotary classifier. However, the pressurizing mechanism becomes expensive due to the divided arrangement of the accumulator, and a large motor must be used with low efficiency. Furthermore, the control system itself becomes complicated. On the other hand, the present invention is a device that suppresses vibration by devising only the hardware of the crushing section, so it is very advantageous from the viewpoint of total cost reduction.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a roller mill equipped with a roller arm support device according to the present invention.

FIG. 2 is a configuration diagram of a roller arm support shaft device.

FIG. 3 is a configuration diagram of a roller arm support shaft device.

FIG. 4 is a configuration diagram of a roller arm support shaft device.

FIG. 5 is a comparative characteristic diagram of roller movement.

FIG. 6 is a schematic diagram showing the movement of a roller.

FIG. 7 is a schematic diagram showing the movement of a roller.

FIG. 8 is a comparative characteristic diagram of amplitude changes with respect to coal hold-up in the mill.

FIG. 9 is a comparative characteristic diagram of changes in product fine particle size with respect to coal feeding amount.

FIG. 10 is a comparative characteristic diagram of the amount of wear of the crushing roller.

FIG. 11 is a schematic diagram for explaining problems in the conventional example.

FIG. 12 is a schematic diagram for explaining problems in the conventional example.

FIG. 13 is a comparative characteristic diagram of vibration displacement of a roller.

FIG. 14 is a characteristic diagram of vibration amplitude for a dimensionless in-mill coal hold-up.

FIG. 15 is a configuration diagram of a roller arm pivot device according to a conventional example.

[Explanation of symbols]

1 Raw material 2 Raw material supply pipe 3 (representative; the same applies hereinafter) Rotary table 4 Grinding roller 5 Roller arm 6 Roller rotation shaft 7 Arm lever 8 Pressure device 9 Support shaft 10 Support shaft support 11 Housing 12 Table rotation shaft 13 Grinding ring 14 Grinding race 15 Compressed powder layer

Claims (4)

[Claims] Claim 1: A rotary table that rotates around a vertical axis on a plane, and is supported in a cantilever manner by an arm from the mill housing side, and a circumferential grinding surface is formed on a powder layer of raw material to be ground on a grinding race. In a roller mill that compresses and grinds the raw material to be crushed using multiple crushing rollers that rotate under pressure, the distance between the cross-sectional center axis of the crushing roller and the support axis of the arm, that is, the length of the pendulum-like movement area, is determined for each crushing roller. A roller arm spindle device for a roller mill, characterized by having different features. 2. The roller arm support device for a roller mill according to claim 1, wherein the lengths of the pendulum-like movement ranges are constituted by arms having different lengths. 3. In claim 1, the deviation of the length of the pendulum motion area of each grinding roller is set to be at most 3.
A roller arm spindle device for a roller mill, characterized in that the spindle is 0%. 4. In claim 1, the set load applied to each crushing roller is adjusted so that the effective loads applied to the powder layer on the table by the crushing rollers having different pendulum motion range lengths are equal. A roller arm spindle device for a roller mill characterized by: