JPH0780335A - Mill and its operation - Google Patents

Abstract

PURPOSE:To provide a technique, by which a symptom of the generation of self-excited vibration in a mill is grasped to surely predict the generation. CONSTITUTION:When the possible generation of self-excited vibration is judged by a phenomenon that a powder layer is easily broken down by the unstable vertical operation of a tension rod 8 which is an object to be monitored for the generation of vibration, for a compressed layer under pulverizing rollers 1 in a pulverizing layer, at least one of measures (a) to make the powder layer thicker or far thinner, (b) to slightly secure humidity and (c) to make grading coarse, is taken. These measures are performed by controlling operating conditions of a classifier 21 (revolution for a rotary type, vane opening for a cyclone type), pressing force of the pulverizing rollers 1, the quantity and temp. of primary air for classifying pulverized raw materials, etc., or the injecting operation of water to raw coal, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mill for finely pulverizing a solid fuel or raw material, and more particularly to a mill equipped with a monitoring device for judging signs of occurrence of self-excited vibration, and based on this monitoring result. The present invention relates to a method of operating a mill that avoids the occurrence of self-excited vibration.

[0002]

2. Description of the Related Art In a coal-fired boiler, low-pollution combustion (low NOx, high-efficiency combustion) and flexible operation (expansion of change in coal supply amount) are carried out in the same manner as other fuels, and pulverized coal machines ( Hereinafter, a solid raw material pulverizer represented by coal may be abbreviated as a mill.), So that higher performance is required. As one type of mill that grinds lumps such as coal, cement raw materials or new raw materials into small pieces, a rigid roller mill equipped with a rotating grinding table and multiple rollers is used, and recently one of the representative models. While solidifying its position as.

This type of mill is driven by a motor having a speed reducer in the lower part of a cylindrical housing, and has a substantially disk-shaped crushing table that rotates at a low speed on a horizontal plane, and its upper peripheral portion in the circumferential direction. It is equipped with a plurality of crushing rollers that rotate by being pressed by hydraulic pressure or springs to equally divided positions. The object to be crushed supplied from the supply pipe (chute) to the center of the crushing table draws a spiral trajectory on the table due to the rotation and centrifugal force of the crushing table and moves to the outer peripheral portion to crush the crushing table. It is crushed by being caught between the race surface and the crushing roller. The hot air sent from the duct is guided to the base of the mill housing, and the hot air is blown up from the air throat between the outer peripheral portion of the crushing table and the inner peripheral portion of the mill housing. The pulverized and produced powder and granules are dried while rising in the mill housing by the hot air blown from the air throat.
The granular material transported to the upper part of the mill housing falls from the coarse one due to gravity (primary classification), and it does not fall, and the slightly fine granular material that penetrates there is a cyclone separator or Classified again by a rotary classifier, fine powder having a predetermined particle size or less is conveyed by hot air, and in the case of a boiler, is fed to a pulverized coal burner or a fine powder storage bin. Coarse powder having a predetermined particle size or more that does not pass through the classifier falls on the grinding table and is ground again with the raw material just supplied to the mill. In this way, the crushing roller repeats the crushing.

[0004]

When the roller mill is to be operated in a wide area load, the vibration of the mill is a problem in devaluing the load. This vibration phenomenon is complicated and its detailed mechanism has not been clarified. However, it is a kind of frictional vibration (stick / slip motion known as a representative of discontinuous / non-linear vibration) caused by the slip between the coal bed and the roller. Is considered to be. As the type of vibration, because the excitation source cannot be clearly specified,
In addition, since the vibration waveform has a spike shape, it can be said to be a type of self-excited vibration. With normal coal, this self-excited vibration becomes severe during low-load operation (conditions in which there is little hold-up of coal in the mill), but depending on the type of coal, it may occur even at considerably high loads.

As a problem of this self-excited vibration, in addition to the effect of the vibration itself, the sign of its occurrence is difficult and difficult to bite, that is, there is no method of monitoring the vibration occurrence potential. For example, even if the speed reducer is provided with an accelerometer or a vibrometer for measuring amplitude, it is difficult to grasp the sign of occurrence of self-excited vibration. Although the condition that the probability of occurrence of self-excited vibration is high is "when the mill is operated in a specific area where coal hold-up in the mill decreases," the occurrence of self-excited vibration is stochastic. This is a phenomenon, and self-excited vibration does not necessarily occur even if the conditions are met. Further, the occurrence of self-excited vibration is affected not only by the coal hold-up in the crushing section in the mill but also by the coal species, the particle size of the coal powder layer, or the dry state of the powder layer, so it is not easy to predict the vibration generation.

The self-excited vibrations in the roller mill are generated by the three crushing rollers almost at the same time, as shown in FIG. 6 or FIG. ) Since it is a phenomenon that it vibrates in the vertical direction, it can be said that the vibration is quite sudden. Therefore, the characteristic such as “the dominant component is gradually amplified as the generation limit is approached” which is often seen in other self-excited vibrations is not seen. The monitoring of self-excited vibration generation potential in the roller mill, as described above, finds a particularly important one among the operations of various equipments of the roller mill in order to find a condition that makes it easy to swing the head so that the crushing roller is displaced laterally. It is considered important to use it as a monitoring parameter.

FIG. 18 shows an example of the prior art (Japanese Patent Laid-Open No. 63-2.
No. 42356), a method of detecting the lift amount of the crushing roller based on the movement of the hydraulic cylinder is shown. The control system of the mill shown in FIG. 18 includes a hydraulic pump 1201 and an oil tank 1.
202, hydraulic cylinder 1203, solenoid valve 120
4, roll lift detector 1205, controller 1206, roll 1207, bawl 1208, segment 1209,
Roll load lever 1210, hydraulic piston rod 1211,
The roll load lever rotating shaft 1212 is configured. Then, the roll 1207 and the segment 1209 placed on the bawl 1208 are floated without touching the metal 1207. Therefore, the roll 1207
When the biting of the raw material (1) into the coal phase 1213 is insufficient, the roll 1207 moves in the vertical direction violently,
After all, the mill will vibrate. Such a roll 12
It is the essence of this prior art to detect the motion of 07. In this conventional technique, since the roll 1207 is supported as a mere cantilever, a change in the thickness of the coal seam 1213 below the roll 1207 is indicated by the roll lift detector 1.
It is detected by 205.

On the other hand, in the roller mill to which the present invention is applied (for example, FIG. 1), the crushing roller 1 is formed into an equilateral triangle (see FIG. 2) via the roller pivot 4 which serves as a pendulum shaft. Is centrally supported in. Therefore, the vertical movement of the tension rod 8 in the present invention is not limited to the mere thickness of the coal layer below the crushing roller 1.
It represents the pendulum motion of the grinding roller. The pendulum movement of such a grinding roller is shown in FIGS. 19 and 20. At the time of so-called pre-excitation before the self-excited vibration starts, as shown in these figures, the pressure frame 1906 (or 2006) and the spring frame 1907 (or 2).
007) periodically swings at a 120 ° pitch (360 rollers / 3 = 120 ° because there are three rollers and three tension rods). At this time, the crushing roller 1901 (or 2001) periodically makes a large pendulum movement ((c) and (d) in the figure. When such movement occurs, as a result, the tension rod (19)
08 (I) and 1908 (II) or 2008 (I) and 2008 (II)) move largely in the vertical direction ((a) and (b) in the figure). Incidentally, the periodic whirling motion as a sign of the occurrence of such self-excited vibration is relatively slow, but when the pendulum motion of the crushing roller ((c) in the figure) approaches the limit, The crushing roller suddenly moves outward with a rapid acceleration, and the self-excited vibration rapidly grows. The fundamental difference from the prior art shown in FIG. 18 is that the support structure of the crushing roller is fundamentally different. Therefore, the results from the displacement gauge, which appear to be similar in appearance, represent a completely different behavior of the grinding roller.

On the other hand, a so-called ring ball mill (often called "E mill" as a model name) of a type in which a plurality of balls roll while being pressed by an upper ring on a rotary table, is also applied. ,
Self-excited vibration occurs due to the friction of the coal seam. In the case of this ring ball mill, the conditions under which self-excited vibration is generated are different from those of the ring balls described above, and they tend to occur during high-load pulverization with a lot of coal hold-up in the mill. During high-load crushing, the balls roll (revolve) on the rotary table without rotating smoothly while contacting each other, so that the balls become violently subjected to frictional vibration in which rotation and slip are alternately repeated. The self-excited vibration of this ring ball mill is also strongly influenced by the frictional characteristics of the raw material powder layer, as in the case of the roller mill. That is, on the table, the vibration level rises when the powder layer of the raw material under the balls or between the balls is fine or the powder layer is dry.

In the above-mentioned prior art, the crushing roller is cantilevered, whereas the mill of the present invention has a crushing roller supporting mechanism for pendulum motion, or a mechanism for rolling a plurality of pressure ring balls. The cause of self-excited vibration of the roller mill or the ring ball mill, which is the object of the present invention, and its countermeasure have not been known at all. Therefore, an object of the present invention is to provide a method capable of grasping a sign of occurrence of self-excited vibration in a mill and reliably predicting occurrence thereof.

[0011]

The above object of the present invention can be achieved by the following constitution. That is, a crushing means for crushing the raw material, a pressurizing means for applying a load to the crushing means, a receiving portion for the raw material which receives the supplied raw material and supports the load by the crushing means, and the crushed raw material In a mill equipped with a classification means for classifying by air flow according to the particle size, a detection means for detecting the displacement amount of the pressurizing means, and the classification condition of the classification means based on the detection result of the displacement amount of the detection means, the pressurizing means Mill, equipped with a control means for controlling at least one of the amount of pressurization, the amount of air for classification, the temperature of air for classification, and the amount of water injected into the crushed raw material, or crushing while applying a load to the raw material via the pressure means. Then, in a mill that classifies the crushed raw material by an air flow according to the particle size, when the displacement amount of the pressurizing means reaches a predetermined value, the classification degree, the pressurizing amount of the pressurizing means, the air amount for classification, the classification For air temperature or grinding A mill operating method for controlling at least one of injection quantity of the charges.

Here, (1) when the mill is a roller mill, the crushing means is a crushing roller, and the pressure applying means presses and holds the crushing roller from above, and an upper end portion of the pressure frame. It is composed of a cylinder rod for connecting a load for crushing the raw material to the crushing roller by connecting and pulling it downward and applying a pressure of the pressurizing medium, and a tension rod connected at its lower end to the cylinder rod. The receiving part consists of a crushing race provided on the turntable,
The detecting means for detecting the displacement amount of the pressurizing means is a displacement gauge for detecting the vertical displacement of the tension rod, and the control means is such that the vertical displacement of the tension rod is at least 1.2% or more of the diameter of the crushing roller. The condition to reach
Determined as a condition requiring caution against the occurrence of self-excited vibration, and when the vertical displacement of the tension rod reaches the above threshold value of 1.2% or more, the number of revolutions of the classifier, the pressure applied to the cylinder rod, and the amount of classification air. , A configuration in which at least one of the temperature of the classification air and the amount of water injected into the pulverized raw material is switched to an operation in which the vertical displacement of the tension rod is reduced.

(2) When the mill is a ring ball mill, the crushing means is a ring ball, and the pressing means is an upper ring for pressing and holding the ring ball from above and a ring lever integrally connected to the upper ring. And a hydraulic cylinder that is connected to the ring lever and presses it downward to transmit the load for crushing the raw material to the ring ball and apply the pressure of the pressurizing medium. The raw material receiving part is provided on the rotary table. It is composed of a lower ring, and the detection means for detecting the displacement amount of the pressurizing means is a displacement gauge for detecting the vertical displacement of the ring lever. The condition that reaches at least 1.2% or more is discriminated as a condition requiring caution for occurrence of self-excited vibration, and the vertical displacement of the ring lever is the above threshold 1.2. At the time of reaching the above, at least one of the vane opening of the classifier, the pressure of the cylinder rod, the amount of air for classification, the temperature of classification air, and the amount of water injected into the pulverized material is displaced in the vertical direction of the ring lever. It is possible to adopt a configuration in which the operation is switched to reduce the operation.

[0014]

[Operation] The unstable vertical movement of the tension rod (in the case of a roller mill) or ring lever (in the case of a ring ball mill) of which vibration is to be monitored is caused by the swinging of the crushing roller in the case of the roller mill, or in the case of the ring ball mill. Is caused by the inclination of the upper ring, that is, the action of lateral displacement on the race around the spindle of the grinding roller due to the collapse of the coal bed under the grinding roller. Before the self-excited vibration, the swinging of the grinding roller is not synchronized. That is, the oscillating phases of the crushing rollers are different. The swinging of the crushing roller is caused by the collapse of the compressed powder layer located below the crushing roller and sandwiched between the crushing roller and the crushing race. That is, the fact that the self-excited vibration is likely to occur means that the compressed powder layer is easily collapsed and the crushing roller is rolling sideways.

As described above, the compressed powder layer is likely to be collapsed in the compressed powder layer in the crushing section (1) to have a specific thinness. (2) It is dry. (3) Fine particles. This is a case where at least one of the above conditions is met. In addition, even if the conditions under the crushing roller or ring ball (thickness, dry state, etc.) are the same,
When fine particles locally flow into the biting part of the crushing roller or ring ball (front side, that is, the central axis side of the rotary table), this may trigger the particle layer to easily collapse during biting. is there.

Therefore, the powder layer is likely to collapse due to unstable vertical movement of the tension rod (in the case of a roller mill) or the ring lever (in the case of a ring ball mill), and it is judged that self-excited vibration may occur. In this case, the operation opposite to the above (1), (2) and (3) is applied to the compression layer under the crushing roller or the ring lever in the crushing section, that is, (a) is the powder layer thickened? Or make it much thinner. (B) Slight humidity is secured. (C) Coarse grain size. Take at least one of these measures.

As described above, the countermeasures are as follows: operating conditions of the classifier (rotation speed in the case of rotary type, vane opening in the case of cyclone type), pressurizing amount of pressurizing means, air amount for classification, classification This is done by controlling the temperature of the air for use or the amount of water injected into the crushed raw material. The same can be done with a ring ball mill,
In this case, while monitoring the inclination of the upper ring of the ring ball mill, adjust the operating conditions of the classifier, the amount of pressurizing means, the amount of air for classification, the temperature of air for classification, or the amount of water injected into the grinding material. To do.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. 1 and 2 show the structure of a roller mill that employs the coal seam monitoring method of this embodiment and an operation method based on the method. FIG. 1 shows the structure of the roller mill in a cross section passing through the central axis, and is a schematic cross-sectional view taken along line AA of FIG. Further, FIG. 2 shows a crushing portion of the roller mill as a view from above, and is a view looking downward from the line BB in FIG. 1. Since the feature of the present invention lies in the method of monitoring the coal bed, that is, the mechanism of the crushing section in the roller mill, it will first be outlined and the configuration and function of the entire roller mill will be described later. As shown in FIG. 1, the end of the roller shaft 6 of the crushing roller 1 is supported by the roller bracket 2 via a bearing (not shown). In the roller bracket 2, the roller pivot 4 is mounted between the pressing frames 5 via the pivot box 3 on the upper portion of the crushing roller 1, that is, on the extension of the vertical axis. The roller pivot 4 serves as a pressure transmission point from the pressure frame 5 to the roller bracket 2 and finally to the crushing roller 1. Also,
The roller pivot 4 serves as a rotation shaft in the swinging operation of the crushing roller 1 (arrow 1α).

Three crushing rollers 1 are mounted at intervals of 120 degrees in the circumferential direction of the rotary table 12. As shown in FIG. 2, the pressure frame 5 has an equilateral triangle shape, and plays a role of pressing and supporting the three crushing rollers 1 together from above in an integrated structure. A frame arm 7 extends from a position corresponding to each “corner” of the equilateral triangular pressure frame 5. The crushing load is transmitted from the outside of the mill by pulling the frame arm 7 downward. A tension rod 8 is connected to the tip of the frame arm 7. The tension rod 8 is coaxially connected to a piston (not shown) in the hydraulic cylinder 9, and the load is generated by the hydraulic pressure pushing down the piston. Depending on the state of the compressed powder layer below the crushing roller 1, the tension rod 8 moves up and down even when the same hydraulic pressure is applied. In this embodiment, such a movement of the tension rod 8 in the vertical direction is measured by the displacement meter 26 (differential transformer type or potentiostat type). Since the case of the hydraulic cylinder 9 is fixed to the anchor, the main body of the displacement gauge 26 is fixed here.
On the other hand, the rod (differential transformer type) or the wire (potentiostat type) of the displacement gauge 26 is fixed to the tension rod 8 which moves in the vertical direction.

The overall structure and function of the roller mill will be described below. The raw material 23 is supplied from a raw material supply pipe (center chute) 22 provided on the central axis of the upper part of the mill, and drops onto the rotary table 12 rotating at the lower part of the mill. Centrifugal force acts on the crushing raw material 18 on the rotary table 12, is supplied onto the crushing ring 13 on the outer periphery of the rotary table 12, is scribed on the upper surface of the crushing ring 13, and has a substantially arc-shaped cross section. Then, the powder is crushed by the crushing roller 1 to form a compressed powder layer 19. The powder generated by crushing penetrates between the throat vanes 14,
While being dried by the hot air 15 blown into the mill,
Transported above the mill. The coarse particles fall on the rotary table 12 due to gravity (primary classification), and are crushed again in the crushing section. The particle group penetrating the primary classification part is centrifugally classified by the rotary classifier 21 (secondary classification). The relatively coarse particles are blown to the inner wall of the mill housing 20 by centrifugal force, and are dropped by gravity to be reground. The fine particles penetrate between the blades of the rotary classifier 21 and are discharged from the product fine powder discharge duct 24 as product fine powder. In the case of coal, it is sent directly to the pulverized coal burner (the hot air 15 becomes the primary air for combustion) or is collected in a storage bin.

FIG. 3 shows an example in which a device for measuring the vertical movement displacement of the tension rod 207 is applied to a roller mill having a mechanism of a pressurizing force generating unit different from the example of FIG. The grinding roller 201 in the housing 212 is the roller bracket 20.
A roller pivot 204 is mounted on a roller bracket 202 between pressure frames 205 via a pivot box 203. In the example of FIG. 3, the tension rod 207 connected to the pressing frame 205 via the frame arm 206 is integrated with the stopper block 211. This stopper block 2
11 moves up and down along the stopper rod 210 integrally with the tension rod 207. A differential transformer type displacement gauge 209 is installed on the stopper rod 210,
The vertical amplitude of the stopper block 211 is measured. A signal from the displacement meter 209 is sent to a control circuit that sets each operation condition of the roller mill. When the crushing roller 201 shakes its head so as to be laterally displaced due to the collapse of the compressed powder layer 217 (arrow β), the roller pivot 204
Position also fluctuates, and the tension rod 207 also unstablely moves up and down (arrow γ).

In the embodiment shown in FIG. 4, the method for installing the pressing force generator and the displacement gauge is the same as that shown in FIG. 3, and the crushing roller 301, the roller bracket 302, the pivot box 303, and the roller in the housing 320 are arranged. The pivot 304 and the pressure frame 305 have the same functions as the corresponding members in FIG. However, FIG.
In the above example, a pressure spring 306 and a spring frame 307 for pressing the pressure spring 306 from above are provided above the pressure frame 305.
The tension rod 309, which is connected to the spring frame 307 via the frame arm 308, pulls the spring frame 307 so as to press it downward, transmits the crushing load to the crushing roller 301, and crushes the crushing raw material 316. In this embodiment, the pressurizing spring 306 is also used for generating the pressing force, but the tension rod 30 is caused by the laterally offset swinging motion (arrow β) of the crushing roller 301.
The unstable vertical movement of 9 (arrow γ) is the same as in the case of FIG.

FIG. 5 shows, based on the signal obtained by the displacement meter,
The outline of the system for changing the operating conditions of the roller mill in order to avoid vibration is shown. From many experiences of measuring the vertical movement of the tension rod with a displacement meter, the swing amplitude (stroke) of the vertical movement reaches at least 1.2% or more of the diameter of the crushing roller, although it varies somewhat depending on the coal type. Then, it is known that the probability of occurrence of self-excited vibration increases. Therefore, this 1.
The operation condition of the roller mill is changed with 2% as the threshold value of the self-excited vibration generation reference. The operation items to be changed are the pressurizing force, the operating conditions of the classifier (rotation speed for rotary type, vane opening for cyclone type), primary air amount, primary air temperature, or raw coal in the coal feeder. Is the amount of water injected into Which operation item is to be changed is determined according to the information on the operation state of the mill. The information is judged based on the mill differential pressure and the grinding power from the process input separately input. Although not shown in FIG. 5, the grinding power and the mill differential pressure (coal bed differential pressure) are used as process inputs for determination.

FIG. 6 and FIG. 7 show an example of a laterally offset swinging motion of the crushing roller due to the collapse of the compressed powder layer. Figure 6
It shows an example in which the lateral displacement amount 1 in the swinging operation (arrow 4α) of the crushing roller 401 is small. In this case, the amount of lowering of the roller pivot 403 is also small. Therefore, the swing amplitude (stroke) of the vertical movement of the tension rod (not shown) is also small. FIG. 7 shows an example in which the oscillating motion of the crushing roller 501 is conversely large and the lateral deviation amount l increases. When this happens,
Compared to the example of FIG. 6, the roller pivot 503 also has a large descending amount, and the tension rod also moves up and down unstablely with a considerably large amplitude.

FIGS. 8 and 9 show vertical vibration states of the crushing rollers 601 and 701 which are caused by the swinging motion of the crushing rollers as shown in FIGS. 6 and 7. The example in FIG. 8 is an example in which the amplitude of vertical vibration (arrow 6γ) is small. Generally, when the amount of lateral displacement at the time of swinging is small, the amplitude of this vibration is also small. On the contrary, in the example of FIG. 9, the crushing roller 701 vibrates vertically with a large amplitude (arrow 7γ). As shown in FIGS. 8 and 9, the crushing roller 60
When 1, 701 self-excited in the vertical direction, the tension rod (not shown) rolls laterally and does not move much in the vertical direction. The up-and-down movement of the tension rod due to the swinging of the crushing rollers 601 and 701 is relatively slow, and the frequency thereof is less than 1 Hz. On the other hand, the crushing roller 60 as shown in FIGS.
The frequencies of self-excited vibrations in the vertical direction of Nos. 1 and 701 are at least 10 Hz or more, which is considerably severe.

FIG. 10 shows a trend of the displacement of the tension rod and the amplitude of the gear box at the time of occurrence of self-excited vibration and immediately before that. The direction in which time advances is
From left to right. The state of the coal seam in the crushing section in the mill changes, and first the vertical movement of the tension rod starts, and its amplitude gradually increases. In this state, the three crushing rollers in the mill are actively swinging independently of each other, although they are not synchronized. The amplitude of the operation of the tension rod is a threshold value as a reference for generating self-excited vibration, that is, approximately 1.2% of the diameter of the crushing roller.
The amplitude of the unstable movement of the tension rod in the vertical direction continues to increase even after reaching 0. In this process, sudden self-excited vibration suddenly occurs, and the amplitude of the gear box suddenly increases. The phases of the three crushing rollers are aligned, and the crushing rollers vibrate violently in the vertical direction in synchronization. During self-excited vibration, the amplitude of the vertical movement of the tension rod is small. As a prelude to the occurrence of self-excited vibrations, the amplitude in the gearbox is quite small, even when the tension rod is actively moving up and down. By the way, as described above, unless attention is paid to the movement of the tension rod, the self-excited vibration gives the impression that it suddenly occurs. When the operating conditions are changed to avoid self-excited vibration, the self-excited vibration disappears. Gradually, the vertical movement of the tension rod also subsides. This is because the compressed powder layer under the crushing roller is stabilized and the swinging of the crushing roller is less likely to occur.

FIG. 11 shows the relationship between the amplitude δ _L of the vertical movement of the tension rod immediately before the occurrence of self-excited vibration and the amplitude δ _OC of the gear box when the self-excited vibration of the crushing roller occurs following this vertical movement. Is shown. Δ _{L on the} horizontal axis is divided by the diameter D _rol of the crushing roller and is expressed dimensionlessly. It can be seen that δ _OC increases at the boundary of δ _L / D _rol ˜0.012. This indicates that, when δ _L / D _rol > 0.012, the self-excited vibration becomes more severe as δ _L / D _rol becomes larger without any measures. On the other hand, if δ _L / D _rol <0.012, δ _OC is extremely small, indicating that substantially no self-excited vibration occurs. When δ _L / D _rol> 0.012 from around [delta] _L / D _rol increases, but the variation of [delta] _OC becomes very large, which is a difference according to the kind of coal. With coal whose powder bed is hard to collapse, even if self-excited vibration occurs, it is not so severe and δ _OC does not become so large.

Table 1 shows by way of example the displacement of the tension rod and the presence or absence of self-excited vibration in a typical mill operation pattern.

[Table 1]

Next, a concrete example of how to change the operating conditions of the mill when the tension rod fluctuates in the vertical direction will be described. Figure 12 is a graph showing vibration characteristic in a roller mill as a concept diagram in relation the coal holdup H _u and amplitude [delta] _oc mill. The amplitude δ _{oc on the} vertical axis is expressed dimensionlessly with reference to the amplitude when the roller and the race are in metal contact with each other in the idle rotation (H _u = 0). When no vibration countermeasure is taken, the vibration characteristic is as shown by the broken line in the figure. In this example, located in the mill in the coal holdup H _u is (A) point, consider the tension rod is unstably moving vertically. Therefore,
Water injection to the coal feeder (0.2-5% (weight ratio) of the amount of coal supplied) or a decrease in the hot air temperature at the mill inlet (decrease at a maximum of 50 ° C relative to the rated inlet temperature, for example 250 ° C) (Fig. Perform the middle arrow (a)). By doing so, the humidity of the coal bed in the crushing portion of the mill is secured even if it is slight, and the coal bed is less likely to collapse. That is, it becomes difficult for violent self-excited vibration to occur. Therefore, even if self-excited vibration occurs, the point (A ₀ ) on the curve of the broken line in the figure
To a point (A ') on the solid line.

The example shown in FIG. 13 shows a vibration avoidance operation by operating the rotary classifier. The particle size of the coal as a parameter as the vibration characteristics, summarizes the relationship of the amplitude [delta] _OC and mill the coal holdup H _u. Vibration characteristics are influenced by the particle size of the mill in the coal holdup H _u and coal seam. More specifically, the vibration characteristics are affected by the thickness of the compressed powder layer under the crushing roller and the particle size of fine powder locally collected in the biting portion of the crushing roller. First, First, consider the case where the mill in a low load operation region where the mill in coal holdup H _u is the (A) are operating. In this case, if the number of rotations of the classifier is reduced, H _u becomes (A) →
It changes to (C), and the amplitude of vibration also decreases. On the contrary, the operation to increase the number of revolutions of the classifier is performed to set _Hu to (A).
→ Even if you try to increase to (D), it does not always work. This is because the circulating particles from the classifying part of the mill are the biting part of the crushing roller, that is, the front surface (center axis side of the rotary table).
If the pulverizing roller bites the fine powder, the compressed powder layer under the pulverizing roller may collapse when the pulverizing roller bites the fine powder.

In the vibration characteristic curve in the figure, the δ _OC value at the point D is low, which is a general tendency, but the probability of occurrence of self-excited vibration is not necessarily low even under the condition of the point D. I have a problem. Particles that circulate from the classifying section of the mill and return to the crushing section are unlikely to be caught in the crushing roller.
That is, when increasing the number of rotations of the classifier, the compressed powder layer under the crushing roller is unlikely to be thick. Therefore, the condition "substantially (as caught in grinding rollers) contribute to milling" H _u is much closer to (A) is from (D) in the figure, i.e., the highest condition: Oscillating probability ( For example, it is considered that the condition is close to (D '). When the mill is operating in a high load region where _Hu is (B) as the initial condition, the classifier rotation speed is changed for the same reason as above. It is more effective to suppress self-excited vibrations by reducing the value of _Hu so that it becomes (C) than by increasing the number of rotations and shifting _Hu to (D).

FIG. 14 shows an example of vibration suppression operation by the operation of reducing the applied pressure. Mill is operated at low load, if the mill in coal holdup H _u is (A), the first increase pressure, H _u is decreased to (C), also reduced the amplitude of the vibration. On the other hand, when the pressing force is decreased, the pulverizing ability is decreased and _Hu is also increased (D), but at the same time, the compressed powder layer under the pulverizing roller is thickened. Since such a thick powder layer is less likely to collapse, self-excited vibration is less likely to occur and the amplitude is also reduced. Next, under high load operation, H
Consider the case where _u is in state (B). In this case, the operation of increasing the pressing force is not preferable in terms of vibration suppression. At the same time as H _u decreases, the compressed powder layer under the crushing roller becomes thin and the coal layer easily collapses, increasing the possibility of severe self-excited vibration (E on the vibration characteristic curve).
point). Therefore, in such a high load operation, it can be said that the operation of reducing the pressing force and shifting to the point D on the vibration characteristic curve is preferable.

FIG. 15 is a conceptual diagram showing an example in which vibration is avoided by increasing / decreasing the primary air amount. When the coal hold-up in the mill _Hu is (I '), when the primary air amount is increased, _Hu decreases and the grain size of the coal bed in the biting part of the crushing roller becomes coarse, so that self-excited vibration occurs. , The amplitude decreases from point I on the α curve corresponding to no countermeasure to point J on the β curve. Here, the α curve is a case where the vibration characteristic is assumed when the grain size of the coal bed bitten into the crushing roller is small. On the other hand, the β curve represents the vibration characteristic when the grain size becomes coarse. Classifying into two types (curves α and β) means that the particle size of the coal bed in the crushing roller biting part in the crushing part changes with H _u , and the fine particle groups are not localized but unevenly distributed. It may not be an accurate taxonomy. However, in order to explain the influence of the grain size of the coal seam on the vibration, it is classified here as two types (curves α and β) for convenience. Here, the two curves α and β are coal hold-up H in the mill depending on the grain size of the coal seam.
_{It is shown} that the size of the vibration generation area based on _u and the vibration level (amplitude, etc.) are affected (if the grain size is fine, it is expanded, and if it is coarse, it is reduced).

Let's assume that the mill is operating under high load and H _u is at (K '). Also in this case, when the primary air amount is increased, H _u decreases and the grain size of the coal in the crushing section also becomes coarse, so that the point K on the α curve shifts to the point L on the β curve and the self-excitation is performed. The amplitude when vibration occurs decreases. Similarly, consider the case where the mill is in a high load operating state and _Hu is in the condition of (M '). Here, the operation of reducing the primary air amount is tried. In that case, H _u increases and the grain size of the coal in the crushing section becomes finer,
Transition from point M on the β curve to point N on the α curve.
Then, the amplitude δ _OC when the self-excited vibration occurs slightly increases. Therefore, it can be said that the operation of reducing the primary air amount is not suitable when the mill is in this state of coal holdup. In addition, reducing the primary air quantity in the conditions in many state of H _u (O '), will be moved in parallel to the P point on the α curve from point O on β curve, the amplitude does not change much . Therefore, it can be said that the effect is poor.

The method of monitoring the coal bed of the mill according to the present invention and the method of operating the mill based on the results are not limited to the roller mill described in the above examples, but a ring ball mill (not a roller mill but a ball as a grinding medium) is used. E for large machines
Often called a type mill) can be applied almost as is. Also in this mill, when the vibration condition is approached, the hydraulic pressure or the operation of the nitrogen cylinder that presses the upper ring that transmits the crushing load from above against the ball may become extremely unstable. In this ring ball mill, vibration increases as the coal hold-up in the mill increases, so an operation to reduce the coal hold-up is required. On the other hand, injecting water into the mill and reducing the primary air temperature are effective in reforming the coal powder layer in the crushing section, because the ball becomes in a slippery state as in the case of the roller mill. FIG. 16 and FIG. 17 show a powder layer monitoring device and a vibration reducing method in which the present invention is embodied and applied to a ring ball mill, respectively.

FIG. 16 outlines the overall structure and function of the ring ball mill. Raw material 1314
Is supplied from a raw material supply pipe (center chute) 1315 on the central axis of the upper part of the mill, and drops onto a rotary table 1303 rotating at the lower part of the mill. Turntable 130
Centrifugal force acts on the pulverized raw material 1311 on No. 3 and is supplied between the upper ring 1302 and the lower ring 1304 on the outer periphery of the rotary table 1303, and compressed and pulverized by the ring balls 1301. The pulverized powder is hot air 130 blown from the ring nozzle 1305 into the mill.
While being dried by 6, it is transported above the mill.
The coarse particles fall on the rotary table 1303 due to gravity and are crushed again by the crushing unit. The particle group penetrating this primary classification part is centrifugally classified by the cyclone classifier 1312 (secondary classification). The relatively coarse particles are blown to the inner wall of the mill housing 1307 by centrifugal force, and are dropped by gravity and re-ground. The fine particles penetrate upward in the cyclone classifier 1312 as indicated by (α) in the figure, and are discharged from the product fine powder discharge duct 1313 as product fine powder.

In the powder bed monitoring apparatus in FIG. 16, the vertical movement (arrow γ) of the ring lever 1302a of the upper ring 1302 is connected to the ring lever 1302a, and the pressurized medium (oil or nitrogen) in the hydraulic cylinder 1308 is connected.
1309 is a device for detecting. The vertical fluctuation amount of the pressurizing medium 1309 is measured by a displacement meter 1310, and the amplifier 131
6. Mill control circuit 1318 via signal processor 1317
Sent to. In the mill control circuit 1318, similarly to the operation output operation unit shown in FIG. 5, operations such as the pressing force, the vane opening of the classifier, the primary air amount, the primary air temperature, and the water injection amount into the raw coal are performed. FIG. 17 is a graph showing the relationship between the amplitude and the amount of coal feeding when the vane opening of the classifier is changed to suppress the vibration as a measure for suppressing the vibration by operating the operation unit.
The amplitude and the coal feed rate are dimensionless values. FIG. 17
As shown in FIG. 5, it is understood that the present invention can be effectively applied to the ring ball mill.

The effects of the above embodiment can be summarized as follows. (1) By monitoring the unstable operation of the tension rod in the vertical direction, it is possible to accurately grasp the sign of occurrence of self-excited vibration. By determining the "preliminary sign" obtained in this way and switching to the operation of vibration avoidance operation, the occurrence of self-excited vibration of the mill can be suppressed in advance. (2) Since self-excited vibration of the mill can be prevented, durability of various peripheral devices including the mill itself is improved. As a result, the reliability of the entire mill in which the mill is used is increased, for example. (3) Low load operation becomes possible, and the minimum load of the mill can be further reduced. This expands the operational range of the mill in which the mill is used, for example. Even in low-load operation, coal burning can be performed, so the consumption of fuel oil for auxiliary combustion can be reduced. Therefore, the entire thermal power plant can be operated more economically. (4) Rapid load increase and load decrease operations are possible without being bothered by vibration. As a result, the responsiveness of the entire boiler in which the mill is used, for example, is significantly improved. (5) In the case where no countermeasure is taken, the situation of vibration generation largely varies depending on the type of coal used, but according to the present embodiment, it is possible to stably operate the mill without causing a vibration problem with any coal. . In this way, the type of coal in which the mill is used, for example applicable to coal-fired plants, is greatly expanded. (6) Since the measuring system of this embodiment is simple and has excellent durability, it can be used without maintenance for a long time.

[0039]

As described above, according to the present invention, the occurrence of self-excited vibration of the mill can be accurately grasped, so that the occurrence of self-excited vibration can be suppressed in advance. for that reason,
Not only the durability of various peripheral devices including the mill itself is improved, but also low load operation is possible, and rapid load increase and load decrease operations are possible without being bothered by vibration. . Based on these effects, the reliability and responsiveness of the entire plant in which the mill is used are significantly improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram (schematic cross-sectional view) of a roller mill in which a roller operation, that is, a powder layer monitoring device according to an embodiment of the present invention is installed.

FIG. 2 is an overall configuration diagram (view diagram) of a roller mill in which a roller operation, that is, a powder layer monitoring device according to an embodiment of the present invention is installed.

FIG. 3 One embodiment of the present invention (application example to a roller mill)
FIG. 3 is a schematic view showing a measuring unit of the monitoring device of FIG.

FIG. 4 is a schematic diagram showing a measuring unit of a monitoring device according to an embodiment of the present invention.

FIG. 5 is a block diagram showing a control system of a vibration suppressing method for a roller mill according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating movement of a roller (lateral deviation) according to an embodiment of the present invention.
The figure which shows typically.

FIG. 7 shows the movement of the roller (lateral deviation) according to the embodiment of the present invention.
The figure which shows typically.

FIG. 8 is a diagram schematically showing the movement of the roller (vertical vibration) according to the embodiment of the present invention.

FIG. 9 is a diagram schematically showing the movement (vertical vibration) of the roller according to the embodiment of the present invention.

FIG. 10 is a diagram showing an example of measurement results of roller movement according to an embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the measurement result of the roller operation and the vibration generation of the roller mill according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram of vibration suppressing operation (water injection, mill inlet temperature) of the roller mill according to the embodiment of the present invention.

FIG. 13 is an explanatory view of vibration suppressing operation (classifier rotation speed) of the roller mill according to the embodiment of the present invention.

FIG. 14 is an explanatory diagram of a vibration suppressing operation (pressurizing force) of the roller mill according to the embodiment of the present invention.

FIG. 15 is an explanatory diagram of a vibration suppressing operation (primary air amount) of the roller mill according to the embodiment of the present invention.

FIG. 16 is a schematic view of another embodiment of the present invention (application example to a ring ball (E type mill)).

FIG. 17 is a diagram showing a relationship between a coal supply amount and a vibration level of a ring ball mill which is another embodiment of the present invention.

FIG. 18 is a schematic view showing a roller movement monitoring device according to the prior art.

FIG. 19 is a view showing a pendulum movement of a crushing roller.

FIG. 20 is a view showing a pendulum movement of a crushing roller.

[Explanation of symbols]

1, 201, 301, 401, 501, 601, 701
... Crushing roller, 5, 205, 305 ... Pressure frame,
8, 207, 309 ... Tension rods, 12, 21
3, 317, 407, 507, 607, 707, 130
3 ... rotary table, 18, 216, 316, 411, 5
11, 611, 711, 1311 ... Grinding raw material, 21 ... Rotary classifier, 1301 ... Ring ball, 1302a ... Ring lever, 1304 ... Lower ring, 1312 ... Cyclone classifier

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

Claims (6)

[Claims] 1. A crushing means for crushing a raw material, a pressurizing means for applying a load to the crushing means, a receiving portion for the raw material which receives the supplied raw material and supports the load by the crushing means,
In a mill equipped with a classifying unit for classifying a crushed raw material by an air flow according to its particle size, a detecting unit for detecting the displacement amount of the pressurizing unit, and a classification unit based on the displacement amount detection result of the detecting unit. A mill equipped with a control means for controlling at least one of classification conditions, the amount of pressure applied by a pressurizing means, the amount of air for classification, the temperature of air for classification, and the amount of water injected into a pulverized raw material. 2. The crushing means is a crushing roller, and the pressing means crushes the raw material by connecting a pressure frame for pressing and holding the crushing roller from above and an upper end portion connected to the pressure frame and pulling downward. It consists of a cylinder rod that transmits the load to the crushing roller and applies the pressure of the pressurizing medium, and a tension rod that connects to the cylinder rod at its lower end, and the raw material receiving part consists of a crushing race provided on the rotary table. The mill according to claim 1, wherein the detecting means for detecting the displacement amount of the pressurizing means is a displacement gauge for detecting the vertical displacement of the tension rod. 3. The control means discriminates a condition in which the vertical displacement of the tension rod reaches at least 1.2% or more of the diameter of the crushing roller as a condition requiring caution for occurrence of self-excited vibration, and the vertical displacement of the tension rod is determined. When the threshold value reaches 1.2% or more, the number of revolutions of the classifier,
At least one of the pressurizing force of the cylinder rod, the amount of air for classification, the temperature of air for classification, and the amount of water injected into the pulverized raw material is switched to an operation for reducing the vertical displacement of the tension rod. The mill described in 2. 4. The crushing means is a ring ball, and the pressing means is an upper ring for pressing and holding the ring ball from above, a ring lever integrally connected to the upper ring, and a ring lever connected to the ring lever and downwardly connecting the ring lever. It is composed of a hydraulic cylinder that applies a pressure of the pressurizing medium by transmitting the load for crushing the raw material to the ring ball by pressing to, and the raw material receiving part consists of the lower ring provided on the rotary table. The mill according to claim 1, wherein the detecting means for detecting the amount of displacement is a displacement gauge for detecting the vertical displacement of the ring lever. 5. The control means discriminates a condition that the vertical displacement of the ring lever reaches at least 1.2% or more of the diameter of the ring ball as a condition requiring caution for occurrence of self-excited vibration, and the vertical displacement of the ring lever is determined. Above threshold 1.2
%, At least one of the vane opening of the classifier, the pressure of the cylinder rod, the amount of air for classification, the temperature of classification air, or the amount of water injected into the pulverized material is adjusted in the vertical direction of the ring lever. The mill according to claim 4, wherein the mill is switched to an operation for reducing displacement. 6. A mill for pulverizing a raw material while applying a load to the raw material through the pressure means, and classifying the pulverized raw material by an air flow according to the particle size, when the displacement amount of the pressure means reaches a predetermined value. , A method of operating a mill for controlling at least one of the degree of classification, the amount of pressure applied by a pressurizing means, the amount of classification air, the temperature of classification air, and the amount of water injected into the pulverized raw material.