JP2941024B2 - Roller mill - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a roller mill for crushing solid raw materials to a predetermined particle size, and in particular, has a feature in a support mechanism of a roller bracket and a crushing roller to suppress vibration of the mill. A roller mill adapted to do so.

[Conventional technology]

In the case of coal-fired boilers, low-pollution combustion (low NOx, reduction of unburned fuel) and wide-area load operation (coal supply change) have been implemented, and as a result, high-performance pulverized coal mills have become required. .

It is a type of crusher that crushes lump such as coal, limestone and other raw materials such as cement raw materials or new raw materials.
A rigid roller mill having a crushing table and a plurality of rollers has been used, and has recently been strengthening its position as one of representative models.

This kind of crusher is a disk-shaped crush table 1115 that is driven by a motor having a reducer (not shown) at the lower part of the cylindrical casing 1118 and rotates at a low speed on a horizontal plane as shown in FIG. 11, A grinding race 1114 that forms an annular groove having a U-shaped cross section is provided on the outer periphery of the upper surface, and is pressed by a hydraulic pressure or a spring or the like to a position on the grinding race that is equally divided in a circumferential direction. A plurality of crushing rollers 1101 that rotate in accordance with are mounted. Grinding table
Pulverized object 1119 supplied from supply pipe 1120 to the center of 1115
Is moved to the outer periphery by drawing a spiral locus on the table 1115 by the rotation of the crushing table 1115 and the centrifugal force thereby, and is caught between the surface of the crushing race 1114 of the table 1115 and the crushing roller 1101. Crushed. Mill casing
Hot air 1117 sent through the duct is led to the base of 1118, and the hot air 1117 forms air between the outer peripheral portion of the crushing table 1115 and the inner peripheral portion of the mill casing 1118. It is blowing up from Throat 1116. The powder produced by the pulverization is dried while rising inside the mill casing 1118 by hot air 1117 blown up from an air throat 1116. The granules transported to the upper part of the mill casing 1118 fall by gravity in order from the coarser one (primary classification), and the finer granules penetrating therethrough are separated by a cyclone separator provided at the upper part of the mill casing 1118 or The powder is re-classified by a rotary classifier including a rotor 1122 and a classification blade 1123, and fine powder having a predetermined particle size or less is conveyed from a product fine powder discharge duct 1125 by hot air 1117, and is sent to a pulverized coal burner or a fine powder storage bin 1 in a boiler. . Coarse particles having a predetermined particle size or larger that do not pass through the classifier are
It falls down and is ground again with the raw material 1119 just fed into the mill. The crushing is repeated by the crushing roller 1101 in this manner.

[Problems to be solved by the invention]

When the roller mill is to be operated with a wide range of load, a problem in reducing the load is mill vibration. Although this vibration phenomenon is complicated and the detailed generation mechanism has not been clarified, the powder layer 1126 and the roller 11
It is said to be a kind of friction vibration (stick-slip motion) caused by the slip of 01. The type of vibration can be considered as a type of self-excited vibration because the excitation source cannot be clearly specified. In ordinary coal, the eighth
As shown in the figure, this vibration becomes intense during low-load operation (conditions with little coal hold-up in the mill), but it may occur even at a very high load depending on the type of coal. The pulverizability of coal that is susceptible to such vibrations varies from good to fairly bad. Therefore, it is generally difficult to predict in advance whether or not vibration is likely to occur based on the pulverizability of coal.

In a typical conventional roller mill shown in FIG. 11, a grinding roller 1101 is supported via a roller bracket 1107 so that the grinding roller 1101 can swing about a roller pivot 1109 as a support shaft. The swinging function of the crushing roller 1101 is very important.When the raw material 1119 is supplied into the mill at the same time when the mill is started, or when the crushing roller 1101 collides with a foreign matter in the raw material 1119, the crushing roller 1101 is tilted. The impact can be absorbed by shaking.

Generally, at the time of high-load grinding, the grinding roller 1101 hardly shakes its head. As described above, when the mill starts or the load increases, the grinding roller 1101
When the crushing roller 1101 is actively engaged, the crushing roller 1101 swings its head.
01 is not synchronized.

On the other hand, when the roller mill vibrates, as shown in FIG. 9, all of the three crushing rollers 901a are simultaneously shifted laterally outward (β) as shown in the crushing roller 901b, and then vibrated up and down as shown in FIG. (Γ). In this case, the three grinding rollers vertically vibrate together in synchronization. Such vibration phenomena are based on the results obtained by the inventors installing a displacement gauge or an acceleration speed in a practical machine mill and measuring when vibration occurs.

From the above, it has been found that in order to suppress the vibration of the mill by devising hardware of the crushing unit, it is important to prevent the three crushing rollers from moving synchronously.

The object of the present invention is to prevent the roller from swaying or vibrating up and down synchronously based on such an idea, and to enable operation in a wide area load or a high coal type without causing strong vibration. To provide a roller mill.

[Means for solving the problem]

The above-mentioned problems of the prior art include a rotating table that rotates in a horizontal plane at a lower portion inside a mill housing, a grinding race engraved on the outer peripheral portion of the upper surface of the rotating table to form an annular groove having a U-shaped cross section, and disposed on the grinding race. A plurality of crushing rollers, a roller bracket provided for each crushing roller and supporting the rollers via a roller shaft, a pressure frame for pressing the roller bracket, and a plurality of crushing rollers provided between each roller bracket and the pressure frame. In a roller mill having a roller pivot for supporting the roller bracket so that the roller bracket can be swung, a roller bracket having a different ratio of each distance from the rotation center axis of the rotary table to the roller pivot and the crushing roller center point, and crushing. Roller mill having a combination of rollers, and mill housing A rotating table that rotates in a horizontal plane at the inner and lower parts, a grinding race engraved on the outer periphery of the upper surface of the rotating table to form an annular groove, a plurality of grinding rollers placed on the grinding race in a pressurized state, In a roller mill having a roller bracket provided for each crushing roller and supporting the roller via a roller shaft, and a roller pivot for supporting the roller bracket so as to be able to swing, from the rotation center axis of the rotary table to the center of the roller pivot. the distance, the difference in distance from the rotation center axis to the grinding roller central axis epsilon is, with respect to the outer diameter D _R of the milling roller, ε = (0.0015~0.03) was constructed as in the range of D _R, and the roller The problem is solved by a roller mill characterized in that the value of ε is different for each combination of the bracket and the crushing roller.

[Action]

If the swinging state of each roller is different in the above configuration, the swinging cycle and amplitude of each roller are different,
The rollers do not make the same movement in a synchronized manner. That is, even if one of the rollers slides on the powder layer for some reason and causes vibration, the other rollers do not synchronize with this. The roller moves so as to at least shift the phase of the swing so as to cancel the movement of the roller that has caused the sliding vibration. In this way, it is possible to prevent a violent vibration in which a plurality of rollers vibrate up and down at the same phase in conjunction with each other.

It should be noted that even if the oscillating support shaft (roller pivot position) is shifted for each roller as in the present invention, the basic crushing performance such as the particle size of the product fine powder or the crushing capacity is not affected.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

The feature of the roller mill according to the present invention lies in the support shaft structure of the grinding roller. Therefore, the support structure of the grinding roller will be described first.

FIG. 2 is a top view of the milling section of the mill (first view).
FIG. 2 is a view taken along the line AA in FIG. 1 and shows the positions of the support shafts (roller pivots 111) of the three grinding rollers 103. As is clear from the figure, the position of the roller pivot 111, which serves as the pivot shaft of each crushing roller 103, in the thickness direction of the crushing roller 103 is different for each crushing roller 103. number 3
FIGS. A to 3C are structural views each showing three grinding rollers as a cross section, and show that the position of the support shaft is changed for each roller.

The center point 319 of the crushing roller 301 shown in FIG. 3A is on the vertical axis 318 that is vertically lowered from the oscillating center axis 309 which is the center axis of the roller pivot 307 toward the crushing ring 313, that is, the roller rotation center axis 304. (The center point 319 in the case of the crushing roller 301.
In the case of FIG. 3A, the center point 319 and the intersection are at the same position. (This is expressed as a sectional view from the side as shown in this figure. In actuality, as shown in FIG. 2, the vertical shaft 318 is Pass on both sides of the center point 319).

As shown in FIG. 3B, the intersection 319 between the roller rotation center axis 304 and the roller cross-section center axis 305 is
The structure is such that the vertical axis 318 comes outside the one shown in FIG. A, that is, inside the mill. In other words, the intersection of the crushing rollers 301 in FIG. 3B is located inside the center point 319. That is, the swing center axis 309 is slightly shifted to the center axis side of the mill as compared with the grinding roller of FIG. 3A. Vertical axis 318, roller rotation center axis 304, and roller section center axis 305
Amount is the distance between the intersection eccentricity epsilon (this distance is the radial direction of the turntable 315) is the approximately as follows the relationship in size between the diameter D _R of the milling roller 301.

ε = (0.0015 to 0.030) D _R ... (1) If ε is too small, it will fall within the manufacturing tolerances. If it is too large, the tuning swing phenomenon can be prevented almost perfectly, but normal rotation The so-called unbalanced rotational vibration at the time (a kind of forced vibration) becomes intense, and the noise may increase.

FIG. 3C shows the configuration of each axis of the remaining grinding roller among the three rollers. The intersection of the crushing rollers 301 is outside the center point 319 of the roller rotation center axis 304 and the roller section center axis 305,
In other words, the intersection has a structure in which the vertical axis 318 comes closer to the housing side of the mill than the center point 319. Swing center axis 309, 3A
Compared to the crushing roller shown in FIG. 3 and FIG. 3B, the crushing roller is shifted toward the mill housing.

By configuring the oscillating support shaft 309 of each crushing roller in this way, it is possible to prevent amplification of a typical self-excited vibration, in which each crushing roller shifts sideways in synchronization and further vibrates vertically. become.

Finally, the overall configuration of the roller mill will be described. FIG. 1 shows a longitudinal sectional view passing through a center axis of a roller mill embodying the present invention. Raw material supply pipe (center chute) that opens downward from above the center axis of the mill
It is supplied from 102 and falls on a rotary table 118 driven by an electric motor via a speed reducer below the mill. On the outer periphery of the rotary table 118, a crushing ring 119 in which a crushing race 120 forming an annular groove having a substantially arc-shaped cross section is engraved is fitted. Centrifugal force acts on the raw material to be crushed on the rotary table 118, moves in the radial direction, is caught by the crushing roller 103, and is crushed. Each crushing roller 103 is not provided with a power source, and is driven to rotate by a frictional force with the raw material that has been caught. The granular material generated by the pulverization is transported to the upper side of the mill by hot air 116 blown from an air throat 117 provided outside the rotary table 118. Of these powders, the coarse ones are turned by the gravity
8. The fine objects that fall on the top (primary classification or gravity classification) are transported further upward. The rotary classifier provided at the top of the mill (this is the classifier shaft 124, classifier rotor 125
And the classification blade 126), the fine powder is further subjected to centrifugal classification (secondary classification). Among the fine powders, relatively coarse ones are blown toward the mill housing 129 by aerodynamic centrifugal action, and the rotary table 118 is used.
It falls down and is crushed again. Only the fine powder from which the coarse particles have been cut passes through the space between the classification blades 126, and is discharged and recovered from the product fine powder discharge duct 128. In a pulverized coal-fired boiler, pneumatic transportation is performed to a pulverized coal burner. In this case, the air 116 blown into the mill serves as about 20% of the total combustion air as primary fuel air. First
In the figure, each grinding roller 103 is supported by a roller bracket 109 via a roller mill rotation shaft 104. In addition, the pressure frame 113 is
Is pressed downward, whereby each crushing roller 103 is pressed down on the crushing race 120 at a predetermined pressure to crush the raw material. A roller-shaped roller pivot 111 is provided between the pressure frame and the roller bracket, and the roller bracket can swing about the roller pivot.

FIGS. 4A to 4C schematically show a state in which each of the grinding rollers in which the pivot position of the roller pivot is changed (assumed) shakes its head so as to slide on the thin powder layer.

In the crushing roller 301 shown in FIG. 4A, the center point between the roller rotation center axis 304 and the roller cross-section center axis 305 is located on the vertical axis 318.
Shake to slide over powder layer 312 on 14. The intersection of the vertical axis 318 and the roller rotation center axis 304 in the grinding roller 301 shown in FIG.4B is supported by being shifted to the left of the figure by ε from the center point of the roller rotation center axis 304 and the roller cross-section center axis 305. (The roller pivot 307 is shifted to the mill center axis side from the example of FIG. 4A). In this case, the grinding roller
4A, the swing radius is slightly smaller than that of the example of FIG. 4A, and it is difficult to swing the neck on the powder layer outside the grinding race 314 (on the side of the mill housing). The crushing surface of the crushing roller 301 is more powder layer 312 than the crushing surface of the crushing roller in FIG. 4A.
Gives strong shearing force to The vertical axis 318 and the roller rotation center axis in the crushing roller 301 showing the support configuration in FIG. 4C
The point of intersection with 304 is supported by being shifted to the right (the housing side of the mill) by ε from the center point of the roller rotation center axis 304 and the roller cross-section center axis 305. Roller pivot 307
Is shifted rearward (to the side of the mill housing) by a small distance. At this time, the crushing roller is easy to swing on the powder layer in a state where the swing radius is slightly larger than that in the example of FIG. 4A. As described above, since the swing radius of each roller is slightly different, it is virtually impossible that each roller swings in the same phase. In this way,
Even when each of the grinding rollers slides on the thinned powder layer, they do not move synchronously because their behaviors are slightly different. For example, if one crushing roller suddenly slides and becomes unstable (prone to vibration), the other crushing roller does not synchronize with its movement. Therefore, it is possible to avoid a vigorous self-excited vibration in which the three crushing rollers shift sideways in conjunction with each other and vibrate vertically. The fact that the vibration of the mill can be suppressed by only slightly shifting the oscillating support shaft 309 in each grinding roller is an economical and effective technique from the viewpoint of manufacturing cost.

Next, the results of a verification test that confirmed the effects of the present invention will be described. FIG. 5 shows the result of examining the effect of the present invention in the case where lime which easily causes vibration is used. For the coal hold-up in a non-dimensionalized mill, the change in amplitude, also expressed in a non-dimensional manner, is summarized. The reference coal hold-up W * is the value when the mill is operated under rated conditions (full load), and the reference amplitude δοε *
Is the measured value at that time. In the case of conventional technology without measures,
It can be seen that the amplitude can be reduced to a considerably low level by employing the roller support mechanism according to the present invention, while violent vibration occurs in the low load zone.

FIG. 6 is for lime which is unlikely to cause vibration, and is a summary of experimental results in the relationship between hold-up and amplitude as in FIG. Even with the conventional technology,
Although the level of vibration was low in the first place, it was confirmed that the amplitude could be reduced in a low load band, albeit a little, by using the present invention.

FIG. 7 shows the result of examining how the crushing characteristics change when the support shaft of the roller is changed as in the present invention. It is summarized by the relation of the differential particle size q to the coal supply amount,
In each case, the dimension is made non-dimensional by the condition C * at the time of rated operation of the mill and the characteristic q * at that time. Although the particle size decreases with an increase in the amount of coal supplied, it can be seen that there is almost no difference in the crushing ability between the spindle structure of the present invention and the conventional one in the entire load range where the experiment was performed. Therefore, it has been confirmed that the roller support shaft structure according to the present invention is very effective in suppressing vibration, and does not sacrifice the crushing ability at all.

Since the oscillating support shafts are different for each crushing roller, the wear state may be different for each crushing roller after long-term use. In this case, the life of the grinding roller can be extended by exchanging the grinding rollers with each other.

The roller mill supporting the roller with the roller pivot of the configuration according to the present invention is not limited to a mill for a coal-fired boiler described as a specific example, but also a mill for oil coke, which is the same solid fuel, and a crushed limestone for desulfurization. It can also be applied to mills for fine grinding of steel slag, non-ferrous refining slag, mills for cement finishing for finely grinding cement clinker, and mills for finely grinding raw materials of various chemical products.

〔The invention's effect〕

According to the present invention, self-excited vibration of the roller mill can be prevented, and particularly, vibration in a low load band can be significantly suppressed, so that a wide range load operation of the roller mill can be performed.

[Brief description of the drawings]

FIGS. 1, 2, 3A, 3B, and 3C show an embodiment of the roller mill according to the present invention, and FIGS. 4A, 4B and 4C show the functions of the mill according to the present invention. Schematic diagrams, FIG. 5, FIG.
FIG. 7 and FIG. 7 are explanatory diagrams of experimental results showing the effect of the present invention,
FIGS. 8, 9 and 10 are diagrams showing vibration characteristics generated in a conventional mill, and FIG. 11 is a structural diagram of a conventional roller mill. 102: Raw material supply pipe, 103: Grinding roller, 108: Roller shaft, 109: Roller bracket, 111: Roller pivot, 113: Pressure frame, 114: Spring, 116: Hot air, 117: Air throat, 118 ... Rotary table, 120 ... Crush race, 121 ... Powder layer, 126 ...
… Classifying blades, 128… Product dust discharge duct, 129… Mill housing.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure-shi, Hiroshima Pref. Inside the Kure Factory, Ltd. (72) Inventor Tadashi Hasegawa 6-9 Takaracho, Kure-shi, Hiroshima Pref. (72) Inventor Yoshinori Taoka 6-9 Takara-cho, Kure City, Hiroshima Pref. Babcock Hitachi Ltd. Inside the Kure Plant (56) References Real Opening 3-22541 (JP, U) (58) Survey Field (Int.Cl. ⁶ , DB name) B02C 15/00-15/16

Claims (3)

(57) [Claims] 1. A rotary table rotating in a horizontal plane at a lower portion inside a mill housing, a grinding race engraved on an outer peripheral portion of an upper surface of the rotary table to form an annular groove having a U-shaped cross section, and a plurality of races arranged on the grinding race. Crushing rollers, a roller bracket provided for each crushing roller and supporting the rollers via a roller shaft, a pressure frame for pressing the roller bracket, and a roller bracket provided between each roller bracket and the pressure frame. A roller pivot having a roller pivot for oscillating the roller, wherein a self-excited frequency of the plurality of crushing rollers is changed for each roller. 2. A rotary table rotating in a horizontal plane at a lower portion inside the mill housing, a grinding race engraved on an outer peripheral portion of an upper surface of the rotary table to form an annular groove having a U-shaped cross section, and a plurality of grinding races arranged on the grinding race. Crushing rollers, a roller bracket provided for each crushing roller and supporting the rollers via a roller shaft, a pressure frame for pressing the roller bracket, and a roller bracket provided between each roller bracket and the pressure frame. Combination of a roller bracket and a crushing roller having different ratios of respective distances from the rotation center axis of the rotary table to the roller pivot and the crushing roller center point in a roller mill having a roller pivot for supporting the oscillating motion of the roller mill. A roller mill comprising: 3. A rotary table rotating in a horizontal plane at a lower portion inside the mill housing, a crushing race formed in an outer peripheral portion of an upper surface of the rotary table to form an annular groove, and a plurality of crushed races mounted on the crushing race in a pressurized state. In a roller mill including a plurality of crushing rollers, a roller bracket provided for each crushing roller and supporting the rollers via a roller shaft, and a roller pivot for supporting the roller brackets so as to be able to swing, the rotation of a rotary table the distance from the central axis to the roller pivot center, the difference in distance to the milling roller center point from said rotation axis epsilon is, with respect to the outer diameter D _R of the milling roller, ε = (0.0015~0.03) in the range of D _R A roller mill, wherein the roller mill is configured as if it were, and the value of ε was different for each combination of the roller bracket and the crushing roller.