JPH081094A - Rotary classifier - Google Patents

Abstract

PURPOSE:To improve the classifying efficiency of a rotary blade type classifier installed above a vertical roller mill or the like. CONSTITUTION:Plural apertures 4a are formed in a lower supporting plate 4, and also a clearance is formed without connecting the lower end part of a straightening cone 5 to the lower end part of a driving shaft 1 thereby securing a passage capable of falling down relatively coarse particles 9a falling down onto the lower supporting plate 4 into a crusher below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary classifier for a vertical roller mill or a dry tube mill for finely pulverizing coal, limestone or the like.

[0002]

2. Description of the Related Art FIG. 4 is a vertical cross-sectional view showing an example of a conventional rotary classifier provided on an upper portion of a vertical roller mill.
Reference numeral (01) is a hollow drive shaft which has a bearing (15) and an oil seal (16) in a rotary sliding portion and rotates around a vertical axis. Reference numeral (2) is a plurality of classification blades arranged symmetrically around the drive shaft (01), and includes an annular upper support plate (3) attached to the drive shaft (01) and a conical lower part. The support plate (04) supports the upper and lower ends, respectively. Reference numeral (05) is an inverted cone-shaped flow straightening cone, the upper edge of which is fixed to the outer peripheral edge of the lower support plate (04) and the lower edge of which is fixed to the lower end of the drive shaft (01). (6) is a coal supply pipe inserted into the hollow portion of the drive shaft (01) with a gap.

When the coal raw material (7) supplied from above the coal supply pipe (6) is crushed by a crushing device (not shown) below the vertical roller mill, the crushed material (8) is conveyed air (not shown). No.) raises the inside of the mill casing (11). Then, it arrives at the rotary classifying device including the drive shaft (01), the classifying blade (2), the upper supporting plate (3), the lower supporting plate (04), the rectifying cone (05) and the like.

Then, the pulverized product (8) is classified into coarse powder (10) and fine powder (9) by the classification blade (2), and the coarse powder (1)
0) drops in the mill and is pulverized again by a pulverizer (not shown) below the mill. On the other hand, fine powder (9) is classified blade (2)
It passes through the space and flows into the rotary classifier. Finer particles (9a) of the fine powder (9) are immediately discharged from the mill outlet pipe (12) while riding on the air flow, but relatively coarse particles (9b) are attached to the ceiling of the mill casing (11). It collides with the inverted conical collision plate (13), stalls, and falls onto the lower support plate (04).

The relatively coarse particles (9b) dropped on the lower support plate (04) move to the outer peripheral side of the lower support plate (04) by the centrifugal force of the rotary classifier, but the carrier air (not shown). It is pushed back and rolled up, and finally comes out as a product from the mill outlet pipe (12).

[0006]

The fine powder that has flowed into the rotary classifier is further classified in the classifier, but the coarse particles separated in the classifier will eventually leave the mill as a product. Therefore, the classification efficiency was low as a whole.

[0007]

In order to solve the conventional problems, the present inventor has arranged a hollow drive shaft rotating around a vertical axis and an axisymmetric arrangement around the drive shaft. A plurality of classification blades whose upper and lower ends are respectively supported by an annular upper support plate and a conical lower support plate attached to the drive shaft, and an inverted conical shape whose upper edge is fixed to the outer peripheral edge of the lower support plate. A rotary classifier installed above the vertical crushing device, comprising: a rectifying cone and a crushing object supply pipe inserted into the hollow portion of the drive shaft with a gap, To propose a rotary classifying device characterized in that a plurality of openings are formed in a supporting plate, and a gap is provided between the lower portion of the rectifying cone and the drive shaft and the pulverized material supply pipe. Is.

[0008]

The rotary classifying device of the present invention is constructed as described above, and a plurality of holes are formed in the lower support plate, and a gap is provided between the lower part of the rectifying cone and the drive shaft and the pulverized material supply pipe. Since the relatively coarse particles that are classified inside the classifier and fall on the lower support plate, most of them pass through the plurality of openings, and further the rectifying cone, the drive shaft, and the object to be ground. After passing through the gap with the supply pipe, it falls to the lower crusher and is crushed again.

[0009]

1 is a vertical sectional view showing an embodiment in which the present invention is applied to a medium-sized mill having a coal throughput of about 20 t / h, and FIG. 2 is a plan view taken along the line II-II of FIG. In these figures, the same parts as those of the conventional one described with reference to FIG. 4 are given the same reference numerals to avoid redundancy, and detailed description thereof is omitted.

In the rotary classifier of this embodiment, a plurality of (eight in the illustrated example) oblong holes (4a) are formed near the outer periphery of the lower support plate (4). Further, the lower end of the drive shaft (1) is not fixed to the rectifying cone (5),
It ends about 50 mm above the lower edge of the inverted cone (5a) of the rectifying cone. A cylindrical portion (5b) having a length of about 300 mm having a gap of about 20 to 30 mm between the straightening cone (5) and the coal supply pipe (6) is formed. Further, the central portion of the inner surface of the rectifying cone (5) and the drive shaft (1) are connected by a plurality of reinforcing pipes (14).

Fine powder (9) passed between the classification blades (2)
Among them, relatively coarse particles (9b) collide with the collision plate (13), stall, and drop onto the lower support plate (4). Then, the centrifugal force associated with the rotation of the classifier moves to the outer peripheral side of the lower support plate (4), and most of it falls from the plurality of openings (4a) formed in the lower support plate (4). After that, it slides down along the inner wall of the rectifying cone (5), and the rectifying cone (5)
Through the gap between the coal supply pipe (6) and the coal supply pipe (6), and falls into a crushing device (not shown) at the lower part of the mill and is crushed again. In the present embodiment, the classifying action in the classifying device can be effectively utilized as described above, so that the classification efficiency of the classifying device is improved.

FIG. 3 shows an example of the result of comparatively testing the classification performance of the present invention and the conventional rotary classifier. The horizontal axis in the figure is 2 in the fine particles (9a) that are the product of the vertical roller mill.
The percentage of weight passed through a 00 mesh (75 μm) sieve is [%], and the vertical axis is the weight ratio on a 100 mesh (150 μm) sieve (based on the percentage of weight passed through a 200 mesh sieve of 70%) [−]. Looking at this figure, the weight on the 100 mesh sieve, which is a representative index of coarse particles, is reduced by about 20% in the present invention as compared with the conventional rotary classifier (that is, the number of coarse particles of 100 mesh or more is small). It is shown that the present invention can provide an excellent rotary classifier.

[0013]

According to the present invention, the classification efficiency of the rotary classifier is improved, and a high performance vertical roller mill can be provided.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a rotary classification device according to an embodiment of the present invention.

FIG. 2 is a plan view taken along the line II-II of FIG.

FIG. 3 is a diagram comparing the classification performances of the present invention and a conventional rotary classifier.

FIG. 4 is a vertical cross-sectional view showing an example of a conventional rotary classifier.

[Explanation of symbols]

 (01), (1) Drive shaft (2) Classification blade (3) Upper support plate (04), (4) Lower support plate (4a) Open hole (05), (5) Rectifying cone (5a) Inverted cone part (5b) Cylindrical part (6) Coal supply pipe (7) Coal raw material (8) Crushed product (9) Fine powder (10) Coarse powder (11) Mill casing (12) Mill outlet pipe (13) Collision plate (14) Reinforcement Pipe (15) Bearing (16) Oil seal

Claims (1)

[Claims] 1. A hollow drive shaft that rotates about a vertical axis, and an annular upper support plate and a conical lower support plate that are arranged axially symmetrically around the drive shaft and are attached to the drive shaft. A plurality of classification blades each having an upper end and a lower end supported, a reverse cone-shaped rectifying cone having an upper edge fixed to the outer peripheral edge of the lower support plate, and a gap inserted in the hollow portion of the drive shaft. A rotary classifier installed above the vertical crusher, which has a crushed object supply pipe, wherein a plurality of holes are opened in the lower support plate, and the lower part of the rectifying cone and the above A rotary classification device, characterized in that a gap is provided between the drive shaft and the pulverized material supply pipe.