JPH0515794A - Roller mill - Google Patents

Abstract

PURPOSE:To enable the operation of a roller mill with respect to wide area load or many kinds of coals without generating vibration by respectively changing the operation positions of the respective stoppers within the same mill to adjust the same and differentiating the gap between a grinding roller and the surface of a grinding race at every grinding roller. CONSTITUTION:The raw material to be ground on a turntable 3 is supplied to a grinding ring 14 to be compressed and ground on a grinding race 15 by grinding rollers 4. When a grinding roller 201 takes in a large amount of the raw material, a stopper fixing jig 210 is operated and a stopper 209 is pushed forwardly to make it possible to largely set the gap between the grinding roller 201 and a grinding race 212. When the stopper 209 is shifted rearwardly to be fixed, the gap between the grinding roller 201 and the grinding race 212 becomes narrow. By this constitution, when the amplitude or frequency of vibration is different at every grinding roller 201, the movement of each grinding roller 201 is cancelled and forced vibratory pendulum motion is generated substantially at random and self-exciting vibration can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller mill for finely pulverizing solid fuel such as coal, limestone, cement clinker or solid raw materials of various chemical products by a rotating table and a pulverizing roller. The present invention relates to a roller mill characterized by the structure of a stopper device or a crushing roller for preventing the generation.

[0002]

2. Description of the Related Art In a coal fired boiler, low pollution combustion (low NO
x, reduction of unburned matter in ash) and wide-area load operation, and the performance improvement of the fine pulverizer (mill) is required accordingly. As one type of mill that grinds lumps such as coal, cement raw material or new raw material raw material, a vertical roller mill that grinds with a rotating table and multiple rollers has become widely used, and recently it has become a representative. It is solidifying its position as one of the models.

This type of mill has a substantially disk-shaped crushing table, which is driven by an electric motor and rotates at a low speed through a reduction gear, at the lower part of a cylindrical housing, and on the upper surface of the outer peripheral portion of the table. It is provided with a plurality of crushing rollers that are rotated by being pressed by hydraulic pressure or a spring or the like at positions equally divided in the circumferential direction. The raw material to be pulverized, which was supplied to the center of the table from the shout, moves to the outer periphery of the table in a spiral shape by centrifugal force on the table, and is caught between the pulverizing race surface of the table and the pulverizing rollers. Be crushed.

Hot air is guided to the lower part of the mill housing through a duct, and this hot air is blown up from an air throat between the table and the housing. The crushed powder is dried while rising in the housing by the hot air blown from the air throat. The granular material transported to the upper part of the housing falls from the coarse material by gravity (primary classification) and is re-pulverized in the pulverization section.

The fine powder particles passing through the primary classifying section are classified again by a cyclone separator or a rotary separator (rotary classifier) provided on the upper part of the housing. The fine powder smaller than the predetermined powder diameter is conveyed by the air flow and is sent to the pulverized coal burner or the fine powder storage bin in the boiler. Coarse particles having a predetermined particle size or more that have not penetrated the classifier fall on the table and are ground again together with the raw material (coal coal) just supplied into the mill. In this way, pulverization is repeated in the mill to produce fine product powder.

[0006]

When the roller mill is to be operated under a low load, the vibration of the mill is a problem in reducing the load. Although this vibration phenomenon is complicated and its detailed mechanism has not been clarified, it is a kind of frictional vibration caused by the slip between the coal seam and the roller (a static friction known as a representative of discontinuous nonlinear vibration).
It is considered to be a slip movement). It can be considered as a kind of self-excited vibration because the vibration source cannot be identified as a vibration type and the displacement waveform of the vibration is spiked.

With ordinary coal, as shown in FIGS. 16 and 31, this vibration becomes severe during low load operation (a condition with a small hold-up in the mill), but depending on the type of coal, it is considerably high load. It may also occur during operation. Coal grindability, which is susceptible to such vibrations, varies from good to fairly poor. Therefore, it is generally difficult to predict in advance whether or not the crushability of coal is likely to cause vibration.

FIG. 19 is a sectional view showing a supporting structure of a crushing roller at the time of initial setting before charging coal.

In this type of roller mill, individual crushing rollers 1401 are held by roller arms 1403 like cantilever beams, and a stopper device 1406 positioned (distance protruding into the mill) by stopper fasteners 1408 is provided. By restraining the downward movement of the roller arm 1403, the crushing surface of the crushing roller 1401 is
A setting gear δ is provided between the grinding races 1412 corresponding to the upper surface of the grinding ring 1411. The gear δ is provided to prevent metal crushing between the crushing roller 1401 and the crushing race 1412 during idle rotation without coal.

In the roller mill in which this type of pressure supporting structure is applied to the crushing roller, the pressure of the crushing roller including the roller arm 1403 is applied by the rotation of the metal touch.
There is a problem that the holding device is easily damaged.

Generally, at the time of high load crushing, the crushing roller 14
01 bites a large amount of raw material, and a thick compressed powder layer 1413 is formed under the crushing roller 1401.
01 lifts the roller arm rotating shaft 1407 as a rotating shaft. In this state, the crushing roller 1401 rotates stably without shaking the neck to crush the raw material. When the crushing roller 1401 actively engages the raw material at the time of starting the coal feeding or when the load increases, the crushing roller 1401 swings its head with the roller arm rotation shaft 1407 as a spindle, but in this swinging operation, The movements of the three grinding rollers are not synchronized (not in phase movement).

At this time, the mill starts to vibrate, but since the crushing roller 1401 is not synchronized, the dominant frequency cannot be specified, and the vibration becomes a so-called forced vibration with a broad frequency distribution, and the operation of the mill is not hindered. .

On the other hand, in the case of crushing coal, which is liable to vibrate, under a low load condition, as shown in FIG. 17, the thickness of the powder layer caught by the crushing roller and the initial setting gap δ (FIG. 19).
Is almost the same, and the rotation of the crushing roller 1401 becomes extremely unstable. That is, when the crushing roller 1401 and the powder layer are in strong contact with each other, a frictional force acts on the crushing roller 1401, but when the powder layer becomes thin, no resistance acts on the crushing roller and the crushing roller rotates only by inertia. (Stick / slip motion).

When one crushing roller 1401 causes such a vertical pendulum-like movement (α), the crushing roller arm 1403 → collision vibration (β) to the stopper device 1406 → mill housing 1405 → the other two The movement propagates to one crushing roller 1401 and three crushing rollers 1
401 starts the in-phase movement, and the movement of the crushing roller 1401 grows into vigorous self-excited vibration.

From the above, it can be seen that it is essential that the three crushing rollers move in synchronism, that is, the in-phase motion is blocked, in order to prevent it by devising the hardware of the crushing section. .

FIG. 38 is a sectional view showing a supporting structure of a conventional grinding roller. In this type of roller mill, a crushing roller 1501 is swingably supported by a roller bracket 1502 with a roller pivot 1503 as a spindle.

This swinging function is very important, and when the crushing roller 1501 bites in a foreign substance such as an iron piece that is difficult to be crushed, the crushing roller 1501 can avoid an impact by shaking its head. When the grinding roller 1501 and the grinding race 1513 are worn, this swinging function also has a self-adjusting function of finding an appropriate pressing position (positional relationship between the grinding roller 1501 and the grinding race 1513).

Generally, at the time of high load crushing, the crushing roller 15
01 almost never shakes his head. As mentioned above,
When the crushing roller 1501 actively bites the raw material when the mill is started or when the load is increased, the crushing roller 1501 shakes its head, but the movements of the three crushing rollers are not synchronized in this swinging operation. At this time, the mill vibrates, but since the crushing rollers 1501 are not synchronized, the dominant frequency cannot be specified, and the frequency distribution is broad, so-called forced vibration, and does not hinder the operation of the mill.

On the other hand, when the rollers vigorously vibrate by self-excitation, as shown in FIG. 32, all three grinding rollers 1001 laterally shift outward (β), and then vibrate vertically as shown in FIG. 33. . The three grinding rollers vibrate up and down together synchronously (in phase). Such a vibration phenomenon is based on the results of the measurement made by the inventors when a displacement gauge or an accelerometer was installed in a roller mill of a pilot scale and the vibration was measured.

From the above, in order to suppress the vibration of the mill by devising the hardware of the crushing section, it is essential that the three crushing rollers move synchronously, that is, prevent the same phase movement. I know there is.

It is already known that the vibration of the roller mill is caused by the slip of the crushing roller on the powder layer. In the prior art whose structure is shown in FIG. 34, a crushing groove 2206 is provided in the center of the crushing roller 2201 and the compressed powder layer under the roller is divided by devising the shape of the roller to prevent vibration. However, this technique also applies to the crushing grooves 2206 of the same shape for each crushing roller 2201 in the same mill.
However, as described above, there remains a possibility that each crushing roller vibrates in the same phase in synchronization with each other.

On the other hand, in addition to the measures against vibration, the shape of the crushing roller and the rotary table has been devised in order to promote the biting of the raw material to be crushed. Some examples in Figure 3
5, FIG. 36, and FIG. 37. In the example of FIG. 35, the protrusion 23
A stepped liner 2302 provided with 01a is adopted.

In the technique shown in FIG. 36, the crushing rollers are provided with steps so that the rollers 2402 serve as independent crushing surfaces.
And 2403 are configured.

The example of FIG. 37 is substantially the same as that of FIG. 36, but is characterized in that the inclination of the crushing surface is different, and the rollers 2402 and 2403 are independent crushing surfaces.

The object of the present invention is to prevent the crushing roller from oscillating its head in a synchronized manner or to prevent vertical oscillating motion on the basis of the above-described concept, so that the crushing roller can be used in a wide area load or in a multi-carbon type without causing vibration. It is to provide a roller mill that enables the operation of.

[0026]

According to the present invention, in order to solve the above problems, the operating position of each stopper in the same mill is changed and adjusted to adjust the gear gap between the grinding roller and the grinding race surface. Different for each grinding roller.

By doing so, when the mill is operated under a low load, or when crushing a raw material that easily causes vibration,
Even if the crushing rollers move up and down or generate torsional vibration, the crushing rollers in the same mill have different vibration amplitudes and frequencies, so the crushing rollers have the same phase movement (the crushing rollers move synchronously, Which is the main factor in the growth of self-excited vibration).

Further, in the present invention, the following means are taken to solve the above problems. A part or a plurality of portions of the crushing surface of at least one crushing roller in the same mill are engraved in a flat shape, or are built up in a flat shape. And, for each crushing roller in the same mill, the number of the flat engraved surface (or the built-up surface) is different,
Alternatively, the position of the engraving surface (or the buildup surface) in the rotation (circumferential) direction of the crushing roller is changed.

With this configuration, when the mill is operated under a low load, or when crushing a raw material that is liable to vibrate, the crushing roller slides sideways and vibrates vertically, or twists and oscillates with respect to the rotating direction of the rotary table. Even if the crushing occurs, the lateral shift frequency and cycle of each crushing roller in the same mill are different, so the relative movement of the crushing rollers (The crushing rollers move in synchronization, which is the main factor in the growth of severe self-excited vibration. Will be able to prevent).

The present invention is also applicable to a roller mill that supports and pressurizes a crushing roller 1501 as shown in FIG. 38 in a Penzirum type by using a roller pivot 1503 as a spindle, and each crushing roller is independently supported by an arm in a cantilever type. It can also be applied to a roller mill that supports and pressurizes.

[0031]

Even if a pendulum-like motion of each crushing roller in the vertical direction or a rolling torsional vibration with respect to the rotation direction of the table occurs, the amplitude of the crushing roller will not change if the frequency is different for each crushing roller. As a result of mutual interference, they are canceled. Even if the vibration of one crushing roller is self-excited and amplified, it is quickly suppressed by the movement of the other crushing roller.

One of the main causes is that the powder layer under the crushing roller is undulated cyclically, unlike the case of in-phase vibration (due to the vibration of the crushing roller, the powder layer is surrounded by the circumference of the rotary table). This is because thick portions and thin portions with respect to the direction are likely to occur periodically).

A deviation of about 20% in the gap δ between the grinding roller and the grinding race in the same mill is sufficient.
This default gap δ, which depends on the size of the mill, is between 5 and 20 mm. If the standard gear is δ = 10mm
Then, with other grinding rollers, δ = 8 mm or δ =
If it is 12 mm, a sufficient suppression effect against self-excited vibration is produced. If the gear gap δ between the crushing roller and the crushing race is too large, there will be an imbalance in the biting of the raw materials for each crushing roller, and the so-called forced vibration derived from the unbalanced rotation is weak even under conditions where normal crushing should be performed. May occur.

Each crushing roller slides sideways (by the way, according to the present invention, it is also possible to prevent the side slides from moving simultaneously),
Even if vertical vibrations or roll-like torsional vibrations with respect to the rotation direction of the table occur, if the frequency and cycle of each vibration are different for each grinding roller, the movement of each grinding roller is canceled as a result of mutual interference. . Even if the vibration of one grinding roller is amplified by self-excitation, it is immediately suppressed by the movement of the other grinding roller.

One of the main causes is that the powder layer under the crushing roller is periodically undulated, unlike the case of in-phase vibration (due to the vibration of the crushing roller, the powder layer on the crushing race is , As a result of vertical vibration, it is easy to alternate between thick and thin parts in the circumferential direction of the rotary table, or as a result of the swinging motion that shifts laterally, in the width direction of the grinding race). Is.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first aspect of the present invention relates to the structure of a crushing part of a roller mill centering on a stopper device for setting a gear gap between a crushing roller and a crushing race.

2, FIG. 4 and FIG. 6 show the structures of the crushing roller mounted in the mill and its peripheral equipment. Each shows the state at the time of initial setting with no raw material in the mill. The crushing rollers to be improved in the first aspect of the invention are independently supported by roller arms from the mill housing side, and a crushing load is applied thereto.

First, FIG. 2 will be described as an example. The crushing roller 201 is attached to the roller arm 205. The roller arm 205 has a roller arm rotating shaft 208 which serves as a pivot shaft for swinging, and about this point, the crushing roller 201 can move up and down like a pendulum (this becomes violent when vibrating). I'm running. That is, when the crushing roller 201 bites in a large amount of raw material, a thick powder layer is formed below the crushing roller 201, and the crushing roller 201 is lifted upward. Roller arm 205
There is a lever 215 on the upper part of the table, and a crushing load is applied by the pressure device 206.

On the other hand, at the lower part of the roller arm 205, a stopper receiving seat 214 is provided so that the crushing roller 201 and the crushing race do not contact (metal touch).
A stopper 209 is attached to the mill housing 207 so as to support the roller arm 205 and the crushing roller 201 so as to push the stopper receiving seat 214 forward. By operating the stopper fixture 210,
If the stopper 209 is pushed forward, the gear gap between the crushing roller 201 and the crushing race 212 can be set large.

On the contrary, if the stopper 209 is moved backward and fixed, the gears of the crushing roller 201 and the crushing race 212 will be narrowed. When the amount of raw material to be pulverized in the mill decreases, the pulverizing roller 201 tends to descend, and the pressing action from above is restricted by the stopper before the powder layer on the pulverizing race 212 is compressed.

In the roller mill embodying the first invention,
The stopper fixing position is changed for each grinding roller in the same mill, and the initial setting position of each grinding roller is changed. That is, the initial setting gear gap between the crushing surface and the crushing race surface of each crushing roller is different.

In the crushing roller 201 shown in FIG. 2, the initial setting gear δ ₁ is smaller than the other two crushing rollers.

The crushing roller shown in FIG. 4 is one in which the size of the gear δ ₂ is intermediate among the three crushing rollers. The gear gap δ ₃ in the grinding roller of FIG. 6 is the largest in the mill. As a result, because of the relationship of δ ₁ <δ ₂ <δ ₃ (1), specifically, the condition of δ ₁ = × 1.15 <δ ₂ <δ ₃ × 0.85 (2) Thus, the gear cap of each crushing roller is set.
The combination of gears to the extent shown in formula (2) is effective in suppressing self-excited vibration and reducing the forced vibration level, and does not sacrifice the fine powder particle size.

FIGS. 3, 5 and 7 show a state in which the mill is subjected to a high load motion (the crushing roller normally rotates and the mill is extremely quiet). The raw material biting amount of each crushing roller is large, and the powder layer under the crushing roller is thick. Naturally, the gap between the crushing roller and the race is equal to the thickness of the powder layer.

Further, the tip of the stopper 209 and the stopper receiving seat 214 are separated from each other.
09 is not directly helpful. Although the initial setting gear is changed for each crushing roller, the thickness of the powder layer is the same for all crushing rollers during such high load operation. That is, δ _{n 1} = δ _{n 2} = δ _{n 3} (3) Further, equal crushing load is applied to each crushing roller.

Up to this point, the present invention has been directed to a crushing roller having a substantially arc-shaped cross section, but the method according to the first invention is equipped with a crushing roller having a trapezoidal cross section, as shown in FIG. It can be applied almost directly to a roller mill.

Although the order is reversed, the overall structure of the roller mill (FIG. 1) equipped with the roller bracket device according to the first aspect of the invention will now be described.

A raw material 1 is supplied from a raw material supply pipe (center shout) 2 located on the central axis of the upper part of the mill and drops onto a rotary table 3 which rotates at the lower part of the mill. Centrifugal force acts on the raw material to be ground on the rotary table 3 and the raw material is fed onto the grinding ring 14 on the outer periphery of the rotary table 3 and the cross section cut on the upper surface of the grinding ring 14 has a substantially arc shape. On the race 15, the powder is crushed by the crushing roller 4.

The granules produced by crushing penetrate the space between the throat vanes 12 and are blown into the mill by hot air 13
It is transported to the upper part of the mill while being dried. Grain that is considerably coarse falls on the rotary table 3 due to gravity and is re-ground in the crushing section (primary classification). The particle group penetrating the primary classification part is centrifugally classified by the rotary classifier 19 (secondary classification). The relatively coarse particles are blown to the inner wall of the housing 8 by the centrifugal force, fall by gravity and are re-ground.
The fine particles penetrate between the blades of the rotary classifier 19 and are discharged from the product fine powder discharge duct 21 as product fine powder.
In the case of coal, is it sent directly to the pulverized coal burner (hot air 1
3 becomes primary air for combustion) or is collected in a storage bin.

9 and 10 schematically show the movement of the crushing roller during virtual vibration under the condition that the crushing surface of the crushing roller and the crushing race surface are different at the time of initial setting in a slightly exaggerated manner. It is a thing.

FIG. 9 shows an example in which the gear cap is set narrow.
The swing amplitude is large in a state where the crushing roller 601 descends to the lowest point to compress the powder layer (A) and in a state where the crushing roller 601 is the highest and splashes (B). In such an example,
The pendulum-like vertical vibration has a large amplitude and a long cycle, that is, a low frequency.

On the other hand, FIG. 10 shows the movement of the crushing roller 701 at the time of vibration in the example in which the gear is set large. The state where the crushing roller 701 is at the lowest position (Fig. 9).
(The pressure applied to compress the powder layer is smaller than that of the above example) (D)
And the crushing roller 701 has the highest distance and the distance (E) in which the crushing roller 701 is splashed, the amplitude is small and the frequency tends to be high.

As described above, when the amplitude and frequency of vibration (when the vibration is about to occur) are different for each crushing roller, the movement of each crushing roller is canceled, and each crushing roller is forcedly vibrated substantially randomly. It will cause a pendulum movement. In this way, it is possible to prevent vigorous self-excited vibration in which the crushing rollers vibrate vertically in the same phase. Rather than preventing it, the fact that self-excited vibration is caused to immediately disappear is the effective effect of the stopper device according to the first invention.

Such a vibration suppressing mechanism is not limited to the roller mill using the crushing roller whose crushing surface has a substantially arc shape described here, and is also common to the roller mill having a roller having a substantially trapezoidal cross section as shown in FIG. Is.

Next, the results of measuring the frequency distribution in the prior art and the specific examples of the first invention by operating the mill in a low load operation range where vibration is likely to occur will be described.

FIG. 11 shows the frequency distribution at the time of self-excited vibration that occurs when all the grinding rollers and the race gears are the same (prior art), and there is a distinctive dominant frequency. I understand.

On the other hand, FIG. 12 is a frequency distribution of the roller mill embodying the first invention. Frequency is broad,
The distribution is such that it is difficult to specify the frequency at which the acceleration peaks. From the frequency analysis result of FIG. 12, it can be seen that in the roller mill embodying the first aspect of the invention, even if the crushing roller oscillates, their movements are so-called forced vibrations.

The forced vibration based on such unbalanced motion is considerably weaker than the intense self-excited vibration whose frequency distribution is shown in FIG. 11, and does not adversely affect the operation of the mill.

FIG. 13 shows a summary of changes in the amplitude of vibration with respect to the coal holdup in the mill and compares the embodiment of the first invention with the prior art. The amplitude δ _{o c on the} vertical axis is divided by the amplitude δ _{o c} * during rated operation to make it dimensionless. On the other hand, the horizontal axis hold-up W
Is made dimensionless by dividing by the holdup W * when the mill is operated at rated load.

In the prior art, the low load zone (W / W * <0.
25), the amplitude was remarkably large, whereas it was confirmed that the amplitude can be significantly reduced when the gear gap between the grinding surfaces was made different for each grinding roller based on the first invention. In the roller mill having the crushing section structure according to the first invention,
The amplitude increases when W / W * <0.25, which is shown in Fig. 1.
As shown in 2, it is considered to be one type of forced vibration derived from unbalanced rotation.

FIG. 14 shows the change in the particle size of the product fine powder with respect to the amount of coal supplied. The grain size q on the vertical axis is divided by the standard grain size q * at the coal supply amount C * at the rated load and expressed as a relative value. The coal supply amount C on the horizontal axis is also divided by the coal supply amount C * at the rated load and displayed dimensionlessly.

Generally, the grain size q decreases as if it is inversely proportional to the coal feed rate Q. In the example of 1st invention, it turned out that it is substantially equal to the fine powder particle size of the conventional roller mill in the range of almost all coal feeding amount. Even in the rated load operating range, it is considered that the high (relatively) crushing ability of the crushing roller having a narrow initial setting gear and the low (also relatively) crushing ability of the crushing roller having a large initial setting gear were offset. In other words, it is understood that the crushing performance does not make a large difference with the gear adjustment method of the degree embodied in the first invention.

The amount of wear was compared for each crushing roller. The results are shown in Fig. 15 (there is no difference in the amount of wear between the rollers when operating at a high load all the time, but a mill with a high proportion of low load operation or a mill that frequently repeats load changes shows this result. Become).

Of the three grinding rollers, the grinding roller with the smallest initial setting gear has the largest amount of wear, and conversely, the grinding roller with the largest gear has the smallest amount of wear, and the difference is 13%. Is. It is expected that the crushing roller with the smallest gear will compress the powder layer more strongly than any other crushing roller at the time of low load operation, and therefore the wear will be relatively severe.

After a long period of use, the difference in the amount of wear of each crushing roller becomes noticeable, and when it seems that it is rather counterproductive to the suppression of vibrations, the crushing rollers used in the same mill should be kept together. Should be replaced. That is, the crushing roller having the maximum initial setting gear and the crushing roller having the minimum gearing are exchanged without changing the adjustment of the stopper.

The roller mill in which the first invention is embodied with respect to the fine powder particle size and the gears of the crushing roller and the crushing race are adjusted by the stopper has almost no difference from the prior art in the entire load range. The results are shown in Fig. 14.

The roller mill equipped with the stopper device having the structure of the first invention is not limited to the mill for coal-fired boilers described as an example, but 1) a mill for oil coke which is the same fixed fuel 2) limestone for desulfurization 3) Mill for finely crushing steel 3) Mill for finely crushing steel slag and non-ferrous slag 4) Mill for cement finishing to finely crush cement clinker 5) Applicable almost as is to a mill for finely crushing raw materials of various chemical products can do.

The feature of the second invention resides in the structure of the crushing roller, which will be described first and the overall structure of the mill will be described later.

The symmetric crushing roller improved in the second invention is based on the shape having a substantially arcuate cross section as shown in FIG. 38. In the second invention, however, the crushing surface shown in FIGS. As shown in the structure, the crushing surface 1302 of the crushing roller 1301 is provided with a flat surface engraved portion 1303.
The length in the circumferential direction of the crushing roller 1301 of the one flat surface engraved portion 1303 is about 30 ° as the spread angle from the roller rotation shaft 305 (FIG. 23).

The plane engraved portion 1303 is formed by the crushing roller 1
The crushing roller 130 is a flat surface in the width direction of the 301.
1 has a substantially arcuate roundness in the circumferential (rotational) direction. However, the radius of curvature of the roundness in the circumferential direction is larger than that of a normal crushing surface, that is, close to a plane.

Further, as shown in FIG. 24, the length of the flat engraved portion 1303 in the width direction of the crushing roller 1311 is about a quarter (1 / th) of the width (or thickness) w ₀ of the crushing roller 1301. 4w ₀ ). If the flat engraved portion is molded to this extent, the crushing roller will be able to move on the powder layer of the raw material to be ground when the position for compressing the powder layer changes from a position other than the flat engraved portion to the flat engraved portion. , It becomes possible to shake the head sideways.

If the plane engraved portion is too small, a swinging motion that tends to cause side slip is less likely to occur. On the other hand, if the plane engraved portion is too large, the crushing roller may not be able to recover to the normal position after sliding outward (toward the mill housing), and the noise associated with the irregular rotation increases.

FIG. 25 and FIG. 26 are two examples showing the position of the flat surface engraved portion in three crushing rollers in the same mill. In the embodiment shown in FIG. 25, the number of flat surface engraved portions 1303 is (a) -1, (b)-
2, (c) -3 places were changed. In the crushing rollers of (b) and (c), the position of the flat surface engraved portion 1303 is provided at every 90 ° with respect to the rotation direction of the crushing roller.

In the embodiment shown in FIG. 26, each crushing roller is provided with two flat surface engraved portions 1303, but the relative positional relationship between the two flat surface engraved portions 1303 is different for each crushing roller.

In the crushing roller (a), the flat surface engraved portion 13
03 are adjacent to each other at 90 ° (or 270 °), and a phenomenon in which normal rotation continues for a long time appears after lateral slips continue at a relatively short interval in one rotation. On the other hand, in the crushing roller (c), two flat surface engraved portions 1303 are provided at positions separated by 180 °, and each crushing roller 1301 makes a half-slip motion.

In the next section, the performance comparison between the embodiment of the second invention and the prior art will be made (FIGS. 28, 29 and 30). The case of using the crushing roller having the structure shown in FIG. The present invention is represented by two invention examples.

Up to this point, an embodiment in which the crushing curved surface of the crushing roller is scraped off to form a flat surface portion has been described. However, a similar flat surface portion is formed on the crushing surface 1602 of the roller by the raised flat surface portion 160.
It is also possible to perform padding molding as No. 3. FIG. 27 shows its structure.

Although the order is reversed, the entire structure of the roller mill equipped with the crushing roller according to the second aspect of the present invention (see FIG. 2).
0) will be described. The raw material 101 is supplied from a raw material supply pipe (center shout) 102 located on the central axis of the upper part of the mill, and falls on a rotary table 103 rotating at the lower part of the mill. Centrifugal force acts on the raw material to be crushed on the rotary table 103, and the raw material is fed onto the crushing ring 123 on the outer periphery of the rotary table 103, and the cross section cut on the upper surface of the crushing ring 123 has a substantially arc shape. It is compressed and crushed by the crushing roller 104 on the race 124.

The pulverized powder and granules pass through the throat vanes 122 and are blown into the mill.
It is transported to the upper side of the mill while being dried by 21. Grain that is considerably coarse falls on the rotary table 103 due to gravity and is re-ground in the crushing section (primary classification). The particle group penetrating the primary classification part is centrifugally classified by the rotary classifier 117 (secondary classification). The relatively coarse particles are blown to the inner wall of the housing 120 by a centrifugal force, fall by gravity and are re-ground. The fine particles penetrate between the blades of the rotary classifier 117, and as product fine powder, the product fine powder discharge duct 11
Emitted from 8. In the case of coal, it is sent directly to the pulverized coal burner (the hot air 121 becomes the primary air for combustion) or is collected in a storage bin.

21 and 22 schematically show the crushed state by the curved crushing surface and the crushed state by the flat surface engraving portion 1205, respectively. In the case of the curved crushing surface as shown in FIG. 21, the imaginary contact center point a on the crushing roller side and the imaginary contact center point a ′ on the crushing race 1206 side are interposed via the compression powder layer 1203.
Are on the central axis 1204 of the roller cross section.

On the other hand, when the crushing roller rotates and the flat surface engraved portion 1205 compresses the powder layer, the swinging motion (α) occurs due to the slip due to the flat surface portion, and during normal crushing ( After swinging from the virtual contact center point aa 'in A), the virtual contact center point slightly shifts to bb' after swinging (B).

As described above, in the crushing roller embodying the second aspect of the present invention, the crushing roller is forcibly caused to perform the lateral movement-like swinging motion. In addition, since the position and the number of the plane engraved portions that cause the laterally-displaced swinging motion are changed for each crushing roller, each crushing roller causes the swinging motion substantially randomly.

In this way, it is possible to prevent the vigorous self-excited vibration of the crushing roller swinging its head in the same phase and vibrating up and down. Rather than preventing it, it can be said that the function of the crushing roller according to the second aspect of the present invention is that the self-excited vibration is caused to disappear instantly.

The effect of the operation of the crushing roller described above is obtained for a crushing roller having a crushing curved surface engraved in a flat shape as shown in FIGS. 20 to 26. FIG. 27, which is a plank overlay on top
The same can be obtained with a crushing roller such as.

FIG. 28 summarizes the change in the amplitude of vibration with respect to the coal holdup in the mill and compares the embodiment of the second invention with the prior art. The amplitude δ _{o c on the} vertical axis is made dimensionless by dividing by the amplitude δ _{o c} * at the time of metal touch (idle rotation without any coal). On the other hand, the holdup W on the horizontal axis is made dimensionless by dividing by the holdup W * when the mill is operated at the rated coal feed rate.

The results of this experiment were obtained when crushing coal which is susceptible to vibration. In the prior art,
While the amplitude is remarkably large in the low load zone (W / W * <0.25), it was confirmed that when the crushing roller according to the second invention is used, the vibration can be significantly reduced. .

Even in the roller mill using the crushing roller according to the second aspect of the invention, the amplitude is slightly large when W / W * <0.25, but this is considered to be one type of forced vibration.
In the second embodiment of the present invention, the amplitude at the time of metal touch is slightly larger than that of the prior art. This is considered to be due to unbalanced vibration, which is so-called forced vibration, due to the random fluctuating load generated by the action of the flat surface engraved portion of the crushing roller according to the second invention.

FIG. 29 shows the test results using coal which is less likely to cause vibrations. Both axes are made dimensionless in the same manner as in FIG. 28, and the relationship between holdup and amplitude is summarized.
Compared with the example of coal that is prone to violent vibration as shown in FIG. 28, although the amplitude is considerably smaller in the conventional technique,
Even so, the vibration of δ _{o c} / δ _{o c} * <3.2 still occurs. On the other hand, if the crushing roller embodying the second invention is adopted, the amplitude δ _{o c} can be lowered to a considerably low level.
It can be seen that

FIG. 30 shows the change in the particle size of the product fine powder with respect to the amount of coal supplied. Particle size q of the vertical axis is represented as a relative value is divided by the reference fine granularity q * in the conventional mill when * Rated coal feed amount Q _c. The horizontal axis is also divided by Q _c * to make it dimensionless. Generally, the grain size q decreases as if it is inversely proportional to the coal supply amount Q.

In the embodiment of the second invention, it was found that the particle size of the fine product powder was almost the same as that of the conventional roller mill. In other words, it can be seen that the crushing performance is not significantly different when the structure of the crushing roller is improved to the extent that it is embodied in the second invention.

With respect to the fine powder particle size, the roller mill having the crushing roller according to the second invention has almost no difference from the prior art in the entire load range. Results are shown in FIG.

The roller mill equipped with the crushing roller according to the second invention is not limited to the mill for coal-fired boiler described as an example, but 1) a mill for oil coke, which is the same fixed fuel, and 2) limestone for desulfurization. Mill for pulverizing 3) Mill for pulverizing steel slag and non-ferrous slag for smelting 4) Mill for cement finishing for pulverizing cement clinker 5) Applicable to mill for pulverizing raw materials for various chemical products be able to.

[0093]

According to the roller mill of the first invention,
The following effects can be achieved. The roller arm support device for a roller mill according to the present invention has the following effects. (1) It is possible to prevent the vibration of the mill due to the slip of the roller. This improves the durability of various equipment including the mill itself. In addition, the reliability of the entire thermal power plant is increased. (2) Low load operation is possible, and the minimum load of the mill can be further reduced. This expands the operation range of the boiler. Since it is possible to burn coal exclusively in the low-load operation region, it is possible to reduce the consumption of fuel oil for auxiliary combustion. Therefore, the entire thermal power plant can be operated more economically. (3) Coal that particles are easily broken flat and are more likely to vibrate violently, coal that easily adheres to rollers and races,
Alternatively, even coal that has a high calorific value per unit weight and tends to operate with a low load on the mill can be operated without causing vibration. In this way, the range of coal applicable to thermal power plants is greatly expanded. (4) Vibration can also be suppressed by controlling the pressing force and the rotation speed of the table and the rotary classifier. However, the pressurizing mechanism also becomes expensive due to the divisional arrangement of the accumulator, etc., and a large motor must be used under low efficiency conditions. Also, the control system itself becomes complicated. On the other hand, the present invention is an apparatus that suppresses vibrations by devising only the hardware of the crushing unit, which is extremely advantageous from the viewpoint of reducing the total cost.

According to the roller mill of the second invention, the following effects can be obtained. (1) The self-excited vibration of the mill can be prevented. (2) The effect of (1) above improves the reliability and durability of the mill itself and the plant-related equipment around the mill. In addition, the discomfort felt by the employees in the plant is eliminated, and the work efficiency is improved. (3) Vibration can be suppressed in the low load zone, so wide load operation of the entire boiler is possible, not limited to the mill. (4) Specific coal species and solid raw materials that have been feared to be susceptible to vibration can be used without problems. This greatly expands the applicability of the milling material to the mill. (5) Being able to suppress vibration with only simple hardware as in the present invention leads to a significant elimination of mill operating costs. Specifically, maintenance costs for complicated control systems and control devices for avoiding vibration are not required.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a roller mill according to a first invention.

FIG. 2 is a configuration diagram of the stopper device.

FIG. 3 is a configuration diagram of the stopper device.

FIG. 4 is a configuration diagram of the stopper device.

FIG. 5 is a configuration diagram of the stopper device.

FIG. 6 is a configuration diagram of the stopper device.

FIG. 7 is a configuration diagram of the stopper device.

FIG. 8 is a configuration diagram of a stopper device applied to rollers having different shapes.

FIG. 9 is a configuration diagram showing a mechanism of a stopper device.

FIG. 10 is a configuration diagram showing a mechanism of a stopper device.

FIG. 11 is a characteristic diagram of the mechanism of the stopper device.

FIG. 12 is a characteristic diagram of the mechanism of the stopper device.

FIG. 13 is a characteristic diagram of test results.

FIG. 14 is a characteristic diagram of test results.

FIG. 15 is a characteristic diagram of test results.

FIG. 16 is a characteristic diagram for explaining problems of the conventional technique.

FIG. 17 is a configuration diagram of a stopper device for explaining problems of the conventional technique.

FIG. 18 is a configuration diagram of a stopper device for explaining a problem of the conventional technique.

FIG. 19 is a configuration diagram of a stopper device for explaining a problem of the conventional technique.

FIG. 20 is a configuration diagram of a roller mill according to a second invention.

FIG. 21 is a configuration diagram schematically showing the movement of a crushing roller.

FIG. 22 is a configuration diagram schematically showing the movement of the crushing roller.

FIG. 23 is an explanatory diagram showing a structure of a crushing surface of a crushing roller.

FIG. 24 is an explanatory diagram showing a structure of a crushing surface of a crushing roller.

FIG. 25 is an explanatory diagram showing the positions of flat surface engraved portions of three crushing rollers in the same mill.

FIG. 26 is an explanatory diagram showing the positions of flat surface engraved portions of three crushing rollers in the same mill.

FIG. 27 is a configuration diagram of a crushing roller in which a crushing curved surface is scraped off to form a flat surface portion.

FIG. 28 is a characteristic diagram showing test results.

FIG. 29 is a characteristic diagram showing test results.

FIG. 30 is a characteristic diagram showing test results.

FIG. 31 is a characteristic diagram for explaining problems in the conventional technique.

FIG. 32 is a configuration diagram schematically showing the movement of the crushing roller for explaining the problems of the conventional technique.

[Fig. 33] Fig. 33 is a configuration diagram schematically showing the movement of the crushing roller for explaining the problems of the conventional technique.

FIG. 34 is a configuration diagram of a crushing roller according to a conventional example.

FIG. 35 is a configuration diagram of a crushing roller according to a conventional example.

FIG. 36 is a configuration diagram of a crushing roller according to a conventional example.

FIG. 37 is a configuration diagram of a crushing roller according to a conventional example.

FIG. 38 is a configuration diagram of a crushing roller according to a conventional example.

[Explanation of symbols]

1 raw material 2 Raw material supply pipe 3 (representative; same below) Rotary table 4 crushing roller 5 roller rotation axis 6 roller arm 7 Pressurizing device 8 mil housing 9 Stopper device 10 Roller arm rotation axis 11 Stopper fixture 12 throat vane 13 hot air 14 Grinding ring 15 crush race 16 Compressed powder layer 17 Raw material to be crushed 18 table rotation axis 19 rotary classifier 20 dam ring 21 Product fine powder discharge duct

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroaki Kanemoto             6-9 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi             Kure Factory Co., Ltd. (72) Inventor Tadashi Hasegawa             6-9 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi             Kure Factory Co., Ltd. (72) Inventor Yoshinori Taoka             6-9 Takaracho, Kure-shi, Hiroshima Babkotsu Hitachi             Kure Factory Co., Ltd.

Claims (6)

[Claims] 1. A rotary table that rotates about a vertical axis on a plane, and a cantilevered beam supported by an arm from the mill housing side, and a circumferential grinding surface on a powder layer of a raw material to be ground on a grinding race. In a roller mill that compresses and grinds a material to be ground by a plurality of grinding rollers that are pressed and rotated, in order to make the distance (gear) between the grinding surface of each grinding roller and the grinding race surface different, A roller mill characterized in that the operating position of the stopper for adjusting the gear gap between the surfaces is made different for each crushing roller. 2. The roller mill according to claim 1, wherein the deviation of the gears in each crushing roller is 5% or more and less than 30%. 3. A raw material to be ground is composed of a rotary table which rotates on a plane around a vertical axis and a plurality of grinding rollers which are rotated by pressing the circumferential grinding surface against the outer peripheral side upper surface of the rotary table, that is, the grinding race. In a roller mill for compression crushing, one or more crushing curved surfaces of at least one crushing roller are formed by engraving in a flat shape or by overlaying into a substantially flat shape including a surface having a large radius of curvature. And a roller mill. 4. The roller mill according to claim 3, wherein the number of the flat engraving surfaces or the substantially flat surfacing surfaces provided is different for each crushing roller. 5. The crushing roller according to claim 3, wherein the crushing roller has a different installation position of the flat engraved surface or the substantially flat surfacing surface in the rotation (circumferential) direction. Roller mill. 6. The roller shaft according to claim 3, wherein the size of the one flat engraved surface or the substantially flat surfacing surface is 1/24 or more and less than 1/6 per length in the circumferential direction of the roller. A roller mill having a width of ⅛ or more and less than ½ of the direction.