JP3115444B2 - Roller mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller mill and, more particularly, to a roller mill for finely pulverizing a solid material such as coal by a rotating table and a pulverizing roller, wherein a throat ring for blowing hot air into the mill is improved. And a roller mill that suppresses vibration.

[0002]

2. Description of the Related Art In a coal-fired boiler, low-pollution combustion (reduction of NOx, reduction of unburned fuel) and wide-area load operation (coal feed quantity change) have been implemented, and a high-performance pulverized coal machine (mill) has been introduced. Now required. As one type of crusher that crushes lump such as solid fuel represented by coal, cement raw material such as limestone or raw material of new material,
A vertical roller mill having a rotary table and a plurality of crushing rollers is used, and has recently been strengthening its position as one of representative models.

A roller mill of this type is generally provided with a disk-shaped rotary table which is driven by a motor having a speed reducer at a lower portion of a cylindrical housing (container) and rotates at a low speed on a horizontal plane, and an outer peripheral portion of an upper surface thereof. Are provided with a plurality of crushing rollers which are rotated by being pressed by a hydraulic pressure or a spring or the like to a position where the crushing roller is equally divided in a circumferential direction. The raw material supplied from the raw material supply pipe (center chute) to the center of the turntable is
Due to the rotation of the rotary table and the centrifugal force caused by the rotation, the rotary table draws a spiral trajectory and moves to the outer peripheral portion. Hot air sent through the duct is guided to a lower portion of the housing, and the hot air blows up from an air throat between an outer peripheral portion of the rotary table and an inner peripheral portion of the housing. The pulverized powder produced by grinding is
It is dried while rising inside the housing by the hot air blowing 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 the finer granular material penetrating therethrough is separated by a cyclone separator (fixed classifier) provided at the upper part of the housing. Classification is performed again by a rotary classifier (secondary classification), and fine powder having a predetermined particle size or less is conveyed by hot air and sent to a pulverized coal burner or a pulverized coal storage bin in a boiler. Coarse particles having a predetermined particle size or more that do not pass through the classifier fall on a rotary table and are pulverized again together with the raw materials just supplied into the mill. Thus, the crushing is repeated by the crushing roller.

[0004]

When the roller mill is to be operated at a low load, a problem in reducing the load is vibration of the mill. Although this vibration phenomenon is complicated and a detailed mechanism is not clarified, it is considered to be a kind of friction vibration caused by slippage of the coal seam and the roller. The type of vibration can be said to be a type of self-excited vibration because the excitation source cannot be clearly identified and the vibration waveform becomes spike-like. In the case of ordinary coal, as shown in FIG. 12, at the time of low-load operation (a condition in which coal hold-up in the mill is small. As shown in FIG. 11, normally, as the amount of coal supplied decreases, the hold-up also decreases, and (The charcoal layer becomes thinner.)

FIG. 13 is a sectional view showing the movement of a conventional crushing roller. In this type of roller mill, a crushing roller 1006 is supported via a roller bracket 1012 so as to be able to swing around a roller pivot 1014 as a support shaft. This swinging function is very important. When the crushing roller 1006 bites a hardly crushable foreign substance such as an iron piece, the crushing roller 1006 can avoid an impact by shaking its head. When the crushing roller 1006 and the crushing race 1019 are worn, a function of appropriately changing the pressing position, that is, the positional relationship between the crushing roller 1006 and the crushing race 1019, is provided.
There is in the swing structure.

Generally, during high-load pulverization, the pulverizing roller 10
06 hardly shakes his head. As mentioned above,
When the crushing roller 1006 actively engages the raw material when the mill is started or when the load is increased, the crushing roller 1006 shakes its head.
The movements of the individual crushing rollers 1006 are not synchronized. At this time, the mill starts to vibrate, but since the grinding roller 1006 is not synchronized, the dominant frequency cannot be specified, and the frequency is broad so-called forced vibration, and does not hinder the operation of the mill.

On the other hand, when the crushing roller 1006 vibrates violently by self-excitation, as shown in FIG.
All of the three 01 are laterally shifted outward (β) almost simultaneously as shown by the solid line, and then vibrate up and down as shown in FIG. 3
The pulverizing rollers 1101 vibrate up and down together in synchronization (in phase). From the above, in order to suppress the vibration of the mill by devising the hardware of the crushing unit, it is important that the three crushing rollers 1101 move synchronously, that is, to prevent the in-phase movement. Recognize.

An object of the present invention is to prevent the crushing roller from swinging or oscillating up and down synchronously based on the above-described concept, and to avoid a wide area load or a high coal type without causing vibration. An object of the present invention is to provide a roller mill having a rotary table and a hot air blowing throat connected to the rotary table, which can be operated.

[0009]

According to a first aspect of the present invention, there is provided a rotary table which rotates around a vertical axis in a lower portion of a rigidly erected cylindrical housing.
A plurality of crushing rollers for pressing and crushing the raw material entrained between the rotary table and the crushing surface, and a gas that is provided over the entire outer periphery of the rotary table and that conveys the crushed raw material upward in the housing. In a roller mill provided with a throat ring device having a large number of throat vanes, at least one of the inclination angle and the interval of the throat vanes is irregularly varied with respect to the circumferential direction of the rotary table. And a roller mill.

According to a second aspect of the present invention, a rotary table that rotates around a vertical axis in a lower portion of a rigidly erected cylindrical housing is engaged between a rotary table and a crushing surface of the rotary table. A plurality of pulverizing rollers for pressing and pulverizing the raw material, and a throat device having a plurality of throat vanes disposed along the outer periphery of the rotary table and injecting a gas for conveying the pulverized raw material upward in the housing are provided. In the roller mill, at least one of the inclination angle and the gap of the throat vane of the throat device is made different from each other in the circumferential direction of the rotary table, and a rule for making the difference is not set to be equal to an integral multiple of the number of crushing rollers. And a roller mill characterized by:

[0011]

In order to solve the above-mentioned problem, the present invention employs a method in which the inclination angle of the rotating throat vane or the pitch of the vane is irregularly varied in the circumferential direction. The throat is located in a gap between the rotary table and the mill housing, through which hot air (primary air) is blown. Here, the vane of the rotating throat has a number of so-called blades mounted on the outer periphery of the rotating table. The vanes of this rotating throat rotate integrally with the table. The vane controls the flow direction of hot air (primary air) blown into the mill, and has a strong influence on the flow pattern of the pulverized raw material in the pulverizing section (particularly in the vicinity of the pulverizing roller).

If the inclination angle or pitch of the throat vanes is made irregularly different from the circumferential direction of the rotary table, the direction of the hot air (primary air) blown from the throat also changes with the rotation of the table. Also, the flow form of the raw material around the same grinding roller changes without regularity with the rotation of the table. As described above, when the flow of the pulverized raw material in the pulverizing section changes, the operations of the pulverizing rollers are not synchronized, and severe self-excited vibration is suppressed. As shown in FIG. 14, if one of the grinding rollers in the mill shifts and shakes its head, the other grinding rollers do not follow this movement. That is, the operation of the crushing roller is canceled by the interaction of the independent movement of each crushing roller. This is because the flow pattern of the hot air blown from the throat vane is different in the vicinity of each grinding roller, and the flow state of the powder layer, especially the state of the biting portion that affects the operation of the grinding roller, is different for each grinding roller. Because they are different.

When the inclination angle of the throat vane is small,
In other words, when the throat vane is closer to vertical, the hot air flows along the inclination of the vane and thus tends to blow up the pulverized raw material in the pulverizing section. In this way, when the throat vane is set up, the flow resistance accompanying rotation increases,
The flow rate of the hot air must be ensured, and the pitch of the throat vanes is made slightly larger than the pitch of the throat vanes having other inclination angles. On the other hand, when the inclination angle of the throat vane is increased, that is, when the throat vane is turned down, the hot air flows in a state almost parallel to the rotary table, and acts to push the pulverized raw material of the pulverizing section in the horizontal direction. .

As described above, the flow state of the raw material in the pulverizing section varies depending on the inclination angle of the throat vane.
The slidability of the crushing roller, that is, the laterally displaced swinging motion of the crushing roller that triggers the generation of self-excited vibration as shown in FIG. 14 also changes with the rotation of the rotary table. As described above, such a mutual canceling action of the swinging motion caused by the present invention is particularly effective in a case where the raw material is small in the pulverizing portion, the particle size is small and a soft powder layer is generated, and intense self-excited vibration is likely to occur. It is.

[0015]

FIG. 1 is a sectional view of a roller mill embodying a pulverizing section structure according to the present invention, taken along a central axis. The grinding section of this roller mill is roughly
It comprises a crushing roller 3 and a rotary table 14 as main elements. The feature of the present invention is that the so-called throat vanes 17a and 17b of the so-called rotary throat which are mounted and mounted on the outer periphery of
Is different from the circumference (rotation) direction of the turntable 14, and this will be described first.

2 to 4 show the structure of the throat vane in the roller mill according to the present invention. In any of the examples, the throat vane 202 is inclined, and the lower end of the throat vane 202 is configured to protrude in the rotation direction of the rotary table. In this way, the hot air passes through the gap between the throat vanes 202 with a small pressure loss. That is, the inclined throat vanes have a structure that receives hot air.

FIG. 2 shows the inclination angle θ of the throat vane 202.
₁ and the pitch (interval) l _P1 of the throat vane 202 are both intermediate. As will be described later, in other portions of the rotating throat 201 in the same mill, the inclination angle and pitch of the throat vanes are different from those in this example. In the example shown in FIG. 3, the throat vane 202 is inclined more than the example in FIG. 2 (the inclination angle is θ ₁ <θ ₂ ). In this structure, the hot air 204 may easily penetrate between the throat vanes 202, that is, since the pressure loss is relatively small, the pitch l _P2 of the throat vanes 202 is slightly smaller than the standard l _{P1 of} FIG. Is set to The structure example shown in FIG.
2 has the smallest inclination (the inclination angle is θ ₃
<Θ ₁ <θ ₂ ). In the case of this structure, throat vane 2
02 can be a resistance to the flow of the hot air 204,
In order to reduce this as much as possible, the pitch l _P3 of the throat vane 202 is set larger than l _P1 and l _P2 in the structural examples of FIGS. 2 and 3.

FIG. 5 schematically shows the arrangement area of the throat group having a structure in which the inclination angles are different as shown in FIGS. 2 to 4, as viewed from above the pulverizing section.
The rotating throat has a structure in which the rotating direction of the rotating table 301 is not regular and the throat vanes are arranged with different inclination angles. The arrangement of such a throat group does not have a periodicity equal to an integral multiple of the number of the crushing rollers 302. For example, when the number of the crushing rollers 302 is three, if the periodicity is a multiple of three, the movements of the crushing rollers are synchronized and vibrate in the same phase.

Although the order is reversed, the overall configuration of the roller mill employing the pulverizing section structure according to the present invention will be described with reference to FIG. The raw material 1 is supplied from a raw material supply pipe (center chute) 2 on the center axis of the upper part of the mill, and falls on a rotary table 14 rotating at the lower part of the mill. It is supplied onto a crushing ring 15 on the outer periphery of the turntable 14 and is crushed and compressed by the crushing roller 3 on a crushing race 16 engraved on the upper surface of the crushing ring 15 and having a substantially arc-shaped cross section. . As described above, in the roller mill of the present embodiment, the throat vanes 17a and 17b installed on the outer periphery of the turntable 14 have irregular inclination angles and pitches with respect to the circumferential (rotation) direction of the turntable 14. It is arranged as follows. The powder generated by the pulverization is transported to the upper part of the mill while being dried by the hot air 20 blown into the mill through the throat vanes 17a and 17b. The coarse particles fall on the rotary table 14 by gravity (primary classification), and are again pulverized in the pulverizing section. The particles that have passed through the primary classification section are subjected to centrifugal classification by the rotary classifier 23 (secondary classification). The relatively coarse particles pass between the blades of the rotary classifier 23 and are discharged from the product fine powder discharge duct 25 as product fine powder. In the case of coal, it is sent directly to a pulverized coal burner (hot air 20 becomes primary air for combustion) or collected in a storage bin.

FIGS. 6 and 7 schematically illustrate the flow state in the pulverizing section when the inclination angle θ of the throat vane is large and small, respectively. As shown in FIG. 6, when the inclination angle θ of the throat vane 413 is large, the hot air 4 blown from the rotating throat 412
14 and the pulverized raw material 415 flow in a state closer to being parallel to the rotating table surface, that is, in contact with the rotating table. The pulverized raw material between the two pulverizing rollers 411 flows from the left to the right by the hot air 414 as shown by the white arrow (a) in the figure. On the other hand, the right grinding roller 411
The fine powder generated and discharged by the rotation of the rotary table flows out in the rotating direction of the turntable, but interferes with the flow of the pulverized raw material indicated by the arrow (a) as shown by the white arrow (b). Therefore, when the inclination angle θ of the throat vane 413 is large, the pulverized raw material 1 tends to stay in the pulverized powder generating section (or the pulverized powder outflow section) of the pulverizing roller 411. Therefore, in the rotating throat 412,
In a region where the inclination angle θ of the throat vane 413 is large,
Although locally, the powder layer pressure loss (pressure loss obtained by subtracting the pressure loss passing through the throat portion from the total pressure loss) tends to increase.

On the other hand, as shown in FIG.
3 is small, the direction in which the hot air 424 is blown is relatively nearly vertical.
The raw material is conveyed upward through the gap. Therefore, in this case, the crushing unit (the crushing roller 4)
21) is relatively smaller than the other throat vanes 423. As described above, the positional relationship of the throat vane rotating with the rotary table (the positional relationship with respect to each of the grinding rollers that are disposed at a predetermined location on the rotary table and rotate at that location by the rotation of the rotary table) causes the powder layer in the grinding roller unit to rotate. If the state is different, the laterally displaced swinging state of the grinding roller (FIG. 14) is also different.

As described above, the behavior of the biting portion and the fine powder generating portion of the grinding roller when the neck is sprinkled is
If it changes depending on the positional relationship of the throat vanes having different inclination angles, the three grinding rollers hardly become self-synchronized. In other words, the operation of one crushing roller does not respond to the other crushing rollers in the same phase. In this way, if the movements of the crushing rollers in the mill cancel each other, it is possible to prevent the occurrence of severe self-excited vibration due to the self-synchronization phenomenon.

Next, a description will be given of the result of the reduction in the vibration level obtained by the mutual canceling action of the operation in the crushing roller as described above. FIG. 8 summarizes changes in the amplitude of vibration with respect to coal hold-up in the mill, and compares the embodiment of the present invention with the prior art. The amplitude δ _{0C on the} vertical axis is dimensionless by being divided by the amplitude δ _0C ^* during idle rotation where the crush roller and the crush race make a metal touch. On the other hand, the hold-up W on the horizontal axis is dimensionless by being divided by the hold-up W ^* when the mill is operated at the rated coal supply. This experimental result was obtained when pulverizing coal, which is likely to cause relatively severe vibration due to the influence of coal quality. In the prior art (FIG. 13), the amplitude increases remarkably in a low load range (W / W ^* ８0.38), whereas in the roller mill equipped with the rotating throat section embodying the present invention, the vibration is greatly increased. It has been demonstrated that reduction is possible. Even in the case of the embodiment of the present invention, the amplitude becomes slightly larger in the vicinity of W / W ^* ０．３0.38 than in other hold-up conditions. However, this oscillation has a self-amplifying unique property. It is a type of forced vibration in which the grinding roller does not self-synchronize, instead of excitation vibration.

FIG. 9 summarizes the results when coal is used which is not so severe even if the roller mill vibrates. Also in this example, it is understood that the amplitude can be reduced by embodying the present invention.
When the inclination angle of the throat vane is made different as in the present invention, as described above, since the flow form of the pulverized raw material above the throat vane is different, the wear state of the throat vane may be different after long-term use. There is.
FIG. 10 shows a comparison of the amount of wear for each throat vane having a different inclination angle. The relative wear amount was evaluated by setting the wear amount when the inclination angle of the throat vane was intermediate to “1”. Comparing the relative wear amount with respect to the inclination angle of the throat vane, the difference is at most 2%, and it can be said that the effect of the configuration of the throat vane on the wear is small enough to cause no practical problem.

The roller mill equipped with a throat ring according to the present invention is not limited to a mill for a coal-fired boiler described as a specific example, but a mill for oil coke, which is the same solid fuel, and a limestone for desulfurization, are pulverized. Mills, mills for fine grinding of steel slag and non-ferrous refining slag, mills for cement finishing to finely grind cement clinker, mills to finely grind raw materials of various chemical products, and industrial waste such as FRP (fiber reinforced plastic) waste It can be applied almost as it is to a mill for fine pulverization for recycling.

[0026]

The effects of the present invention are summarized as follows. (1) The occurrence of self-excited vibration of the mill can be prevented. (2) Due to the effect of (1), the reliability and durability of the mill itself and plant-related equipment around the mill are improved. In addition, there is no physical discomfort of the employees in the plant, and work efficiency is improved. (3) Since vibration can be suppressed in a low-load region, low-load operation of the entire boiler can be performed, not limited to the mill. (4) A specific type of coal or solid fuel which has been feared to be easily vibrated can be used without any problem. This greatly improves the applicability of the milled raw material to the mill.

[Brief description of the drawings]

FIG.

FIG.

FIG.

FIG.

FIG. 5 is a diagram showing an embodiment of the present invention.

FIG.

FIG. 7 is an operation schematic diagram of a throat ring unit according to the present invention.

FIG.

FIG. 9 and

FIG. 10 is a view showing the effect of a mill to which the present invention is applied.

FIG.

FIG.

FIG.

FIG. 14 and

FIG. 15 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Raw material 2, ... Raw material supply pipe, 3 ... Grinding roller, 7 ... Roller bracket, 9 ... Roller pivot, 11 ... Pressure frame, 12 ... Pressure spring, 13 ... Spring frame, 14 ... Rotary table, 15 ... Grinding Ring, 16: grinding race, 17a: inclined throat vane, 17b: upright throat vane, 18: seal ring, 19: housing, 20: hot air, 22: compressed powder layer, 23: rotary classifier,
26 ... Air throat.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside the Kure Factory (72) Inventor Hiroshi Yuasa 6-9 Takaramachi Kure City, Hiroshima Prefecture Babcock Day (56) References JP-A-60-12152 (JP, A) JP-A-4-235754 (JP, A) JP-A-4-243551 (JP, A) JP-A-4-310244 (JP, A) JP-A-5-15794 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B02C 15/00-15/16

Claims (2)

(57) [Claims] 1. A raw material bitten between a rotary table rotating around a vertical axis and a crushing surface of the rotary table in a lower portion of a rigidly installed cylindrical housing, and the material is pressed and crushed. In a roller mill provided with a plurality of pulverizing rollers and a throat ring device provided with a plurality of throat vanes which are arranged over the entire outer periphery of the rotary table and inject a gas for conveying pulverized raw material upward in the housing, the throat A roller mill characterized in that at least one of the inclination angle and the interval of the vanes is irregularly varied in the circumferential direction of the rotary table. 2. A rotary table rotating around a vertical axis in a lower portion of a rigidly installed cylindrical housing, and a plurality of materials for pressing and pulverizing the raw material caught between the rotary table and a pulverizing surface of the rotary table. A roller mill provided with a plurality of pulverizing rollers and a number of throat vanes arranged along the outer periphery of the rotary table and for injecting a gas for conveying the pulverized raw material upward in the housing. At least one of the inclination angle and the gap of the throat vane is made different with respect to the circumferential direction of the rotary table, and the rule of making the difference is not set to be equal to an integral multiple of the number of crushing rollers. Roller mill.