JP2742066B2 - Rotary classifier fine crusher - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary classifier-type fine pulverizer having a pulverizing section and a classifying section, and having a rotary classifying function in which a plurality of blades are attached to the classifying section. .

Also in coal-fired boiler, low-pollution combustion (low NO _x, unburned reducing) and rapid load change operation (coal feed quantity change) is performed,
Along with this, a high-performance pulverizer has been required.

As one type of pulverizer for finely pulverizing aggregates such as coal, cement raw materials, or new raw materials, a vertical roller mill equipped with a pulverizing table and a plurality of rollers has been used. is there.

Fig. 12 shows the structure of the vertical roller mill. The vertical roller mill has a disk-shaped rotary table 55 which is driven by a motor having a speed reducer (not shown) at a lower portion in a mill casing 65 and rotates at a low speed on a horizontal plane. A plurality of pulverizing rollers 59 are rotated by being pressed against the equally dividing position by a hydraulic pressure or a spring. The raw material to be pulverized 50 supplied from the raw material supply pipe 51 to the center of the rotary table 55 moves to the outer periphery of the rotary table 55 in a spiral path by centrifugal force generated by the rotation of the rotary table 55. Then, the crushing is performed between the crushing race surface 58 of the rotary table 55 and the crushing roller 59 and crushed.

Hot air 64 sent through a duct (not shown) is guided to the base of the mill casing 65, and this hot air generates air between the outer peripheral portion of the rotary table 55 and the inner peripheral portion of the mill casing 65.・ Blowing up from throat 62. The pulverized particles are dried while rising in the mill casing 65 by hot air 64 blowing up from an air throat 62. The granular material transported to the upper part of the mill casing 65 is classified by a cyclone separator or a rotary classifier 68 provided at the upper part of the mill casing 65, and fine powder having a predetermined particle size or less is discharged from the product fine powder duct 67 by hot air. It is conveyed and sent to a pulverized coal burner or a pulverized storage bin in a boiler (not shown). Coarse powder having a predetermined particle size or more that does not pass through the rotary classifier 68 falls on the rotary table 55 and is pulverized again with the raw material just supplied into the mill. In this way, the crushing is repeated by the crushing roller 59.

In addition, 51 in the figure is a raw material supply pipe (center shot),
52 is a rotary classifier shaft, 53 is a rotary classifier rotor, 54 is a rotary classifier blade, 56 is a rotary table shaft, 57 is a rotary table rotary shaft, 60 is a crush roller shaft, 61 is a crush roller shaft, 63 is a rotary shaft. Air throat vane, 66 is a dam ring.

By the way, as described above, many vertical mills are circulating closed-circuit pulverizing systems with a classifier at the top of the mill, and the performance of not only the pulverizer but also the classifier is maintained while maintaining a strong relationship with the pulverizer. Has a significant effect on the nature of

Recently, a rotary classifier 68 has been widely used as a classifier instead of a cyclone separator. The rotary classifier 68 has a plurality of rotary classifier blades 54 arranged at equal intervals in the circumferential direction on a rotary classifier rotor 53 provided on the mill center shaft, and a drive system independent of the rotary drive system of the rotary table 55. Is rotated by the The powder and granules blown up by the hot air 64 from the mill pulverizing unit again fall into the pulverizing unit due to the centrifugal force of the airflow generated by the rotating classifying blades 54. On the other hand, the fine powder smaller than the predetermined particle diameter passes through between the rotary classifying blades 54 and is discharged from the product fine powder duct 67 to the outside of the mill as product fine powder. There are two main reasons why the rotary classifier 68 has come into wide use.

i) More and more product fines of sharp particle size are required. This requirement is particularly strong in the fields of cement and new materials.

ii) Improvement in responsiveness to load fluctuation is required.
This is mainly for load fluctuation operation of a pulverized coal-fired boiler, and is advantageous only in that the number of rotations can be controlled as compared with a cyclone classifier.

The rotary classifier 68 is provided with a plurality of plate-shaped rotary classifier blades 54 on the rotary classifier rotor 53.The rotary classifier 68 rotates according to the required particle size of the product fine powder, the classification shearing or the load change speed. The design or operation method is set by changing the shape, specification, rotation speed, etc. of the classifying blades 54.

[Problems to be solved by the invention]

In the conventional rotary classifier mill, when the coal feed (crushing) capacity is increased or the number of revolutions of the rotary classifier 68 is increased to improve the classification performance, the mill is moved from the pulverizing section to the classifying section. There is a problem that the gas flow containing a high concentration of particles and the gas flow going down from the classifying section to the pulverizing section collide with each other and form a stagnation portion in the mill casing 65 at the position shown by the oblique lines in FIG. Was. If such particles or airflows remain, the pressure loss in the mill will increase and the blowing power will increase, and the sufficient fineness of the powder required for combustion cannot be obtained. Becomes impossible.

FIGS. 9 and 10 show the structure of a conventional rotary classifying mill to which radial blades are attached. FIG. 11 shows the structure of the inclined blade, and a rotary classifier of this type has also been widely used. FIG. 12 schematically depicts a flow pattern in a conventional rotary classifying mill, in which particles accumulate at an intermediate position between a pulverizing section and a classifying section.

Some prior art attempts have been made to forcibly separate the ascending flow and the descending flow in the mill casing 65, but have not achieved a decisive and sufficient effect.

Japanese Patent Application Laid-Open No. Sho 62-241559 shown in FIG. 13 has a rotating blade 315 having a substantially L-shaped horizontal cross-sectional shape, and rotating blade pockets 315a and 315c formed at the edges, and once captured. This is a device for surely returning the coarse particles 317 to the mill pulverizing section. This concept is considered to be effective in preventing re-scattering due to collision between the particles 317 and the rotating blades 315. In the drawing, 316 is a corner portion, and 318 is a trajectory of a particle.

However, providing the rotating blade pockets 315a and 315c in a bent state near a right angle as in this configuration not only promotes the generation of hydrodynamic airflow resistance but also promotes the retention of particles 317 in the rotating blade region. I have to do it. That is, the pressure loss in the classifying section increases, and the pulverizing ability of the mill may decrease due to an excessive increase in the return coal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotary classifier pulverizer of a pneumatic transport classification type capable of eliminating the above-mentioned problems and obtaining high-quality product fines even during high-load operation.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a pulverizing unit provided at a lower part of a mill casing,
The pulverized material transported with the ascending airflow is classified into coarse powder and fine powder by a rotating classifying blade that is radially or tangentially inclined with respect to a plurality of plate-shaped blades, and is formed at the top of the mill casing. It is intended for a rotary classifier-type pulverizer that takes out fine powder from an outlet.

Then, the diameter of the rotary classifying blade gradually increases toward the mill upper direction, and the tip of the rotary classifying blade in the mill upper direction and the radially outer end is gradually rounded toward the rotation direction of the classifier. It is characterized in that it is bent and a substantially flat straight line is formed below its tip.

[Action]

In the rotary classifier blade according to the present invention, since the tip is inclined or bent with respect to the rotation direction, the powder or granules existing near the classifier blade tip are forcibly absorbed into the center of the rotary classifier. It becomes possible. As a result, it is possible to significantly reduce the particle accumulation area generated in the mill casing. The classifying blade bend is formed in the classifying blade whose diameter increases in the upper direction of the mill (in such a case, the classification of coarse particles starts from the lower side of the classifier and proceeds to the separation of finer particles. Varies), both at the height and in the radial direction of the classifier. This makes it possible to feed only fine particles into the classifier so that coarse particles are suppressed as little as possible in the classifier blade row.

(Example of the invention)

FIG. 1 is an axial sectional view of a rotary classifier pulverizer (hereinafter abbreviated as a mill) embodying the present invention, and FIG. 2 is a view from above a classifier, which is a main part of the present invention.

For example, a raw material 1 to be crushed such as coal is fed from above a raw material supply pipe (center shot) 2 on the center axis of the mill,
It falls on the turntable 3 and is guided by a centrifugal force to a crushing ring 6a mounted on the circumference of the turntable 3. An arc-shaped crushing race 6b is engraved on the upper surface of the crushing ring 6a, and three crushing rollers 7 that roll while being pressed down on the crushing race 6b are equally divided in the circumferential direction of the rotary table 3. (120 mm each). The raw material 1 to be pulverized is pulverized into pulverized coal between the pulverizing race 6b and the pulverizing roller 7 by the compressing and shearing action of the two devices.

The raw material 1 in the form of granular powder is aerodynamically transported to the upper part of the mill casing 13 by hot air 12 blown from an air throat 10 provided on the outer periphery of the turntable 3.
Of these powders, rather large coarse particles are dropped onto the rotary table 3 by gravity (primary classification) without reaching the rotary classifier and are reground. The particles passing through the primary classifier reach the rotary classifier, but relatively coarse particles are driven out of the classifier by aerodynamic centrifugation.
On the other hand, the fine particle group flows between the rotary classifier blades 16 of the rotary classifier and is supplied from the product fine powder discharge duct 18 to a pulverized coal burner (not shown). In FIG. 1, reference numeral 4 denotes a rotary table shaft;
5 is a rotary table rotating shaft, 8 is a crush roller shaft, 9
Denotes a rotating shaft of a grinding roller, 11 denotes an air throat vane, and 17 denotes a dam ring.

The rotary classifier according to the present invention has a cylindrical rotary classifier shaft 14 rotating around the raw material supply pipe 2, a rotary classifier rotor 15 attached to a lower end thereof, and a rotary classifier rotor 15 mounted between the circumferential direction and the like. It is composed of a plate-shaped rotating classifying blade 16.

As shown in FIG. 2, the rotating classifying blade 16 has a tip curved in an arc shape in the rotating direction. This is equivalent to a 'facing section' for allowing the fines remaining at the tip of the classifier to flow into the center of the rotary classifier. Thus, a structure that bends in the direction of rotation tends to induce resistance, but in fact the opposite is true, and aerodynamic resistance or flow resistance due to the presence of particles is surely reduced.

As shown in FIG. 3, the curvature start point of the rotary classifier blade 6 is represented by the ratio of the distance r from the center axis to the outer peripheral direction r to the span R from the central axis of the rotary classifier to the tip of the rotary classifier blade 16 as shown in FIG. This corresponds to the position between / R and 2/3. The starting point of the rotation of the rotary classifier blade 16 in the height direction is determined by the rotation classifier blade.
Half the position from the lower end of 16, that is, h / H in Fig. 4.
That is, the relation of == 1/2 is established. This portion h corresponds to the lower portion of the rotary classifying blade 16 and has a substantially flat straight line as shown in FIG.

The reason why the upper part of the rotary classifying blade 16 is curved in this way is to prevent coarse particles from flowing between the rotary classifying blades 16 and 16. In the rotary classifier, classification of large particles starts from the lower end of the classifier, and is classified into fine particles sequentially as going upward. If the lower end of the rotary classifier blade 16 is curved, even coarse particles will enter between the rotary classifier blades 16, 16, which is a very adverse effect for the purpose of improving the particle size.

FIG. 3 schematically (two-dimensionally) depicts a flow pattern of an air flow between the rotary classifier blades 16 as a horizontal sectional view of the classifier from above the classifier.

As in the present invention, due to the action of the angle of attack provided at the tip of the rotary classifier blade 16, the airflow flows from the tip of the rotary classifier blade 16 so as to be enclosed in the central axis direction of the classifier. Naturally, much of the particles carried by the airflow are also expected to flow between the rotating classifier blades 16,16. FIG. 4 shows such a phenomenon as a trajectory of particles from the side of the rotary classifier. Particles transported from below the rotating classifier are fed from the curved portion at the tip of the rotating classifying blade 16 to the rotating classifying blade 1.
It flows into between 6, 16 and passes through the rotary classifier and is collected as product fines. By the above operation, the particle group flows so as to be enclosed between the rotary classifier blades 16, 16, so that it is possible to prevent the generation of a particle stagnation portion generated at the inlet of the rotary classifier. This prevents excessive circulation and over-grinding of the particles in the mill and allows the mill to operate effectively.

Fig. 5 shows the mill differential pressure (pressure loss) against the coal feed load factor.
Is a test result (pilot mill) showing the change in the above, and compares the performance of the rotary classifier according to the present invention with the performance of the conventional rotary classifier.

When compared at the same coal loading rate, the mill differential pressure is lower in the mill that finely classifies the rotary classifier according to the present invention. This trend is
The service is provided in the entire range of the coal loading load where the experiment was conducted. In particular, the difference between the mill differential pressures of both mills is increased under the condition of high coal loading rate, and the rotary classifier according to the present invention is effective under the conditions of higher concentration of grinding and classification in the mill. You can see that it works.

FIG. 6 shows the change in the mill differential pressure with respect to the classifier rotation speed ratio. In this case, the coal supply load was fixed.

In the conventional rotary classifier, when the number of rotations is increased, the amount of circulating particles in the mill is increased, and the differential pressure of the mill is rapidly increased. On the other hand, in the rotary classifier according to the present invention, due to the action of suppressing the rotary classifier blades 16, no particle stagnation occurs, and the increase in the mill differential pressure is small even under the high rotation speed classification condition.

Figure 7 shows the product fines particle size (20
2 shows the comparison between the performance of the conventional rotary classifier and the performance of the rotary classifier according to the present invention with the change of the remaining ratio of the mesh pass. In general, as the classifier rotation speed increases, the fine powder particle size improves. However, at the rotation speed within the test range, the classifier of the present invention has a higher particle size. This is probably because, as described above, extra circulation in the mill was prevented.

FIG. 8 shows the results of a combustion experiment using pulverized pulverized coal, and proves the results of the present invention.

Write conditions using classifier according to the present invention is NO _x and the ash unburnt both low, it can be seen that a significant combustion improvement occurs. This is because the flame holding is strengthened by the improvement in the particle size of the fine powder, so that a high-temperature combustion region having a low air ratio is stably formed near the burner. That is, it is considered that not only the unburned matter in the ash was reduced due to the promotion of combustion, but also the intermediate product for reducing NO to N ₂ was actively released by rapid thermal decomposition.

As described above, by using the rotary classifier according to the present invention, not only the performance of the mill is improved and the operability is improved, but also high-efficiency combustion with low pollution is realized. Functional improvements will be achieved throughout the plant.

The pulverizer having the rotary classifier according to the present invention is not limited to the mill of the solid fuel-fired boiler such as the fine pulverization or petroleum coke, which has been described as an example, and
It can also be directly applied to a cement finishing mill, a steel slag mill, or as a special purpose, a mill for finely pulverizing ceramic raw materials or a mill for producing pigment and tarwa. Particularly, in the field of cement, recently, particularly strict quality control and energy saving operation are being promoted, so that the rotary classifier-type pulverizer according to the present invention is considered to be particularly effective.

〔The invention's effect〕

According to the present invention, as described above, the diameter of the rotary classifier blade gradually increases as it goes toward the upper part of the mill, and the tip of the rotary classifier blade in the mill upper direction and radially outward is directed in the rotation direction of the classifier. It is characterized in that it is bent, and a portion below the tip is substantially flat and straight.

In this way, by turning the tip of the rotary classifying blade in the mill upper direction and the radially outer end toward the direction of rotation of the classifier so as to have a gentle roundness, the powder particles existing in the vicinity of the classifying blade tip can be bent. The body is forcibly absorbed into the center of the rotary classifier, so that the particle accumulation area generated in the mill casing can be greatly reduced.

Also, by gradually increasing the diameter toward the top of the mill, and making the lower part of the tip portion almost flat straight, coarse particles can be prevented from entering the classifying blade row, and fine particles can be prevented. Only the classifier blades can be greeted.

 The above effects are summarized as follows.

(1) The maximum particle size decreases and the amount of fine powder increases. That is, the particle size of the product fine powder is improved.

(2) In connection with the above-mentioned effect (1), the pulverization capacity that satisfies a predetermined particle size increases. This realizes a compact mill.

(3) In connection with the above-mentioned effect (1), it becomes possible to finely pulverize a variety of raw materials having significantly different hardness and pulverizability and control the particle size of the fine powder.

(4) The amount of circulation in the mill is reduced, and the pressure loss in the mill is reduced.

(5) The flow of the particles between the classification blades becomes smooth, the residence time of the particles at the blade tip and in the vicinity of the mill housing wall surface is shortened, and the abrasion amount of the equipment material can be greatly reduced.

As described above, according to the present invention, it is possible to provide a mill particularly suitable for improving the particle size of fine powder and for energy saving operation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a rotary classifier-type crusher according to an embodiment of the present invention, FIG. 2 is a plan view of a rotary classifier of the fine crusher,
FIGS. 3 and 4 are explanatory views showing the mechanism of the rotation classifying section, FIGS. 5, 6, 7 and 8 are characteristic diagrams, and FIGS. FIG. 11 is a plan view and a sectional view of a classification unit, FIG. 11 is a plan view of another conventional rotary classification unit, FIG. 12 is a schematic configuration diagram of a fine pulverizer, and FIG. 13 is an explanatory view of a conventionally proposed classification unit. is there. 1 ... raw material to be crushed, 3 ... rotary table, 7 ... crushing roller, 15 ... rotary classifier rotor, 16 ... rotary classification blade.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside the Kure Factory, Babkotsuk Co., Ltd. (72) Inventor Yoshinori Taoka 6-9 Takaramachi Kure City, Hiroshima Prefecture Babkotsuk Day (72) Inventor Tadashi Hasegawa 6-9 Takara-cho, Kure City, Hiroshima Prefecture Babkotsukitsu Kure Factory (56) References JP-A-62-258785 (JP, A) JP-A-62 JP-A-258758 (JP, A) JP-A-62-258786 (JP, A) JP-A-62-241559 (JP, A)

Claims (1)

(57) [Claims] A pulverized material pulverized in a pulverizing section provided at a lower portion of a mill casing and transported together with an ascending airflow is rotated by a rotating classifying blade in which a plurality of plate-like blades are radially or tangentially inclined. In a rotary classifier crusher that classifies coarse powder and fine powder and takes out fine powder from an outlet formed in the upper part of the mill casing, the diameter of the rotary classifier blade gradually increases as it goes toward the upper part of the mill. The tip of the rotary classifying blade in the upper part of the mill and radially outward is bent in the direction of rotation of the classifier, and the lower part of the tip is formed into a substantially flat straight line. Crusher.