JPH10180126A - Vertical mill for coarse grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the burning-out time of a boiler by setting the grain size of coal particles of 3mm or smaller on a coarse grain vertical mill applied to a fuel feed system of a boiler. SOLUTION: Raw material coal is fed from a coal feed pipe 1 and crushed by a rotating pawl 6 and a roller 8, and hot air 9 is blown from an annular section 8 to carry a crushed material to an upper section. Annular sections 20, 21 and 22 are formed by lower discharge pipes 12 and 15, conical sections 11 and 14 and cylindrical sections 10 and 13 of an outer hopper and an inner hopper, and grains are flowed up while colliding with the wall faces of the above referred annular sections and rebounding therefrom and again collide with a top plate 10-1, and coarse grains again are dropped down into the inner hopper. On the other hand, fine grains are small in inertia force and flowed up by riding on the air flow to reach a mill outlet. The terminal speed V1 of grains is set as 11m/s or more, by which the fine grains of grain size of 3mm or smaller only can be guided to the mill outlet, while fine grains of grain size of less than 3mm are dropped again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical mill for coarse particles used for drying, pulverization, classification and pneumatic transportation in a fuel supply system for a circulating fluidized bed and a fuel supply system for a pressurized fluidized bed boiler.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing the structure of a conventional vertical mill for coarse particles. In the figure, 1 is a coal feed pipe, 2 is a mill outlet pipe, 3 is a conical portion of a hopper, 4 is a cylindrical portion, 5 is hot air 9
A wind box for sending a, 7 is a drive unit, and these constitute a mill body. Six rotary bowls are provided inside the mill main body, and are driven to rotate by a drive unit 7. A plurality of rollers 8 are fixedly mounted on the upper part of the rotary bowl 6. Reference numeral 9 denotes a hot air blowing annular portion, to which hot air 9a from the wind box 5 is sent.

FIG. 8 is a diagram showing the trajectories of particles and gas in the vertical mill having the above-described structure. In FIG. 8, coal dropped from the upper part of the coal feed pipe 1 falls on the upper surface of the center of the rotary bowl 6. Since the rotary bowl 6 is driven to rotate by the drive unit 7, the coal dropped to the center moves outward by centrifugal force and is pulverized when passing through the roller 8 on the rotary bowl 6, and the pulverized particles are blown out with hot air. It is blown up by hot air 9 a from the annular portion 9 and reaches the mill outlet tube 2.

[0004]

In the above-mentioned conventional vertical mill for coarse particles, at the mill exit, a coal particle size distribution of 3 mm is required.
There is about 20 wt% of coal having a diameter of not less than 20 mm, and a circulating fluidized bed boiler or a pressurized fluidized bed boiler requires a long time to burn out. Therefore, there is a need to reduce the particle size to 3 mm or less. The conventional vertical mill for coarse particles has a problem that it does not meet this need, and it is necessary to reduce the coal particle size at the outlet of the vertical mill to 3 mm or less.

[0005] In addition, although the particle size is set to 3 mm or less, it is also required to supply coal having an appropriate particle size according to the requirements of the boiler side, and the classified particle size may be set to 3 mm or more. It has also been necessary to be able to operate to obtain a particle size.

[0006]

The present invention provides the following means (1) and (2) to solve the above-mentioned problems.

(1) Coal supply pipe for supplying raw coal from the upper part, and an outer pipe which covers the periphery of the outlet part of the coal supply pipe, is arranged axially symmetrically with this, and has an upper part connected to the mill outlet pipe. In a vertical mill for coarse particles, the raw coal supplied from the coal feed pipe is pulverized by a rotary bowl and a roller provided at the bottom in the outer pipe, and the pulverized material is conveyed to the mill outlet pipe by hot air blown from the periphery; The outer pipe has a cylindrical shape in which the upper and lower parts are larger than the central part, and each is connected to the central part by a conical part, a mill outlet pipe is provided in the upper ceiling plate, and a rotating bowl and a roller are provided in the lower part. An outer cylindrical container to be arranged; disposed inside the outer cylindrical container with the same center axis as that of the coal feed pipe at a predetermined interval, with the upper and lower parts opened and the lower part extended to the coal feed pipe outlet end. A vertical mill for coarse particles, comprising an inner cylinder hopper.

(2) In the above (1), the movable member is disposed coaxially close to or in contact with the outer periphery of the upper portion of the inner cylinder hopper, is supported by the coal feed pipe, and can move up and down together with the coal feed pipe. A vertical mill for coarse particles characterized by having a cylinder.

In (1) of the present invention, the coking coal falling from the upper part of the coal feed pipe falls to the center on the rotating bowl, but moves outward by centrifugal force, is pulverized by the rollers, and is removed from around the rotating bowl. It rises due to the hot air that blows up. The rising solid air flow is rectified in the central part between the outer cylinder and the internal hopper, and then collides with the wall due to the inertia of the particles in the conical part and the annular part between the outer cylinder and the internal hopper in the upper cylindrical part. While repeating the rebound at an equal angle, it goes straight upward and collides with the ceiling plate of the outer cylinder container, but coarse particles repel and enter the upper opening of the internal hopper, and the distance between the wall surface of the internal hopper and the coal feed pipe Repeatedly collides and rebounds, falls and is recovered.

[0010] On the other hand, the fine particles collide with the ceiling plate and repel. However, they take on the airflow flowing to the mill outlet pipe, reach the mill outlet pipe, and can collect and supply only the fine particles to the boiler. At this time, by setting the flow velocity of the hot air to a predetermined flow velocity or higher and to be equal to or higher than the terminal velocity at which the particles can float in the air flow, for example, only particles having a particle diameter of 3 mm or less are guided to the mill outlet tube, and particles having a diameter of 3 mm or less Can be collected again in the internal hopper.

In (2) of the present invention, when a movable cylinder is provided on the upper part of the internal hopper, and the movable cylinder is lowered to lower the upper end of the internal hopper, a part of the particles which collide with the ceiling plate and repel and fall are reduced. Instead of entering the internal hopper, it collides again with the outer cylinder container wall, rebounds, and then stalls and is carried by the rising airflow to the mill outlet tube, so the amount of fine particles increases and the coarse diameter increases. Can be increased and varied. When a large particle size is required on the boiler side, the movable cylinder can be lowered to adjust the particle size.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a sectional view showing a configuration of a vertical mill for coarse particles according to a first embodiment of the present invention. In FIG. 1, reference numerals 1 to 9 are the same as those in the conventional example shown in FIG. 7 and will be referred to as they are, and the basic solid air flow is also the same as in the example shown in FIG.
Although the description of this flow is omitted, the characteristic portions of the present invention are portions denoted by reference numerals 10 to 15 and 20 to 22, and these portions will be described in detail below.

In FIG. 1, reference numeral 10 denotes a cylindrical portion above the hopper, which has a ceiling plate 10-1. 11 is a conical portion of the hopper, and 12 is a lower discharge pipe connected to the conical portion 3. These 10, 11, and 12 are connected to the conical portion 3 to form a hopper outer tube. 13 is a cylindrical portion at the upper part of the inner hopper, 1
Reference numeral 4 denotes a lower conical portion, 15 denotes a lower discharge pipe of the inner hopper, and the other configuration is the same as the conventional one.

In the first embodiment of the above construction, hot air 9a at 200.degree. C. is blown at about 70 m / s from the hot air blowing ring 9 around the rotary bowl 6, comes into contact with charcoal, is dried, and is blown upward. Transport.

In the annular portion 20 between the lower discharge pipe 12 and the lower discharge pipe 15 of the inner hopper, the rising solid air flow is straightened and flows straight along with the particles and the air flow. In the annular portion 21 between the conical portion 11 of the hopper and the conical portion 14 of the inner hopper, the air flow slightly flows inward due to centrifugal force, but flows substantially along the passage.

On the other hand, the particles travel straight through the annular portion 20 due to inertial force, collide with the conical portions 14 and 11 and the cylindrical portion 10 at the annular portions 21 and 22, and travel upward while repelling. This state is shown in FIGS. 2 and 3, where FIG. 2 shows the flow of coarse particles and FIG. 3 shows the flow of fine particles. The terminal velocity of the 3 mm particles (the speed at which the particles are floating in the airflow) is represented by v _t so that the particles of 3 mm or less can be transported vertically with the particle size of 3 mm as a branch point, and v
_t ≒ 11 m / s or more. Actually, v _t = 15 m / s
And

FIG. 2 shows the flow of the coarse particles described above. The flow 40 of the coarse particles goes straight between the annular portions 20 and collides with the conical portions 14 and 30 in the annular portion 21, rebounds and repels the conical portions. 11 and 3
1 and also hits at the conical portions 10 and 32 in the annular portion 22 and rebounds, and the ceiling plates 10-1 and 10-3
Collision and rebound at three places. After that, the coarse particles have a large inertial force and do not enter the airflow, but enter the inner cylinder hopper within the cylinder 10 and repeatedly collide with and rebound with 34, 35, 36,
It descends and is collected.

FIG. 3 shows a flow of fine particles, and a flow 41 of fine particles.
Goes straight through the annular portion 20 and, like the fine particles shown in FIG.
0 ', 31', 32 ', and 33' repeatedly strike and rebound, and the fine particles have a low inertia force and rise in the air current. It is led to the outlet pipe 2 and supplied to the boiler.

[0019] The velocity of the particles as described above in the case of the v _t = a 11m / s or more, the particle size is 3mm or more particles are again lowered into the mill as shown in FIG. 2 to the mill outlet pipe 2 The particles having a particle size of 3 mm or less are sent to the mill outlet pipe 2 by an air current as shown in FIG. 3, so that coal particles of 3 mm or less required by the boiler are obtained.

FIG. 4 is a sectional view showing a configuration of a vertical mill for coarse particles according to a second embodiment of the present invention. In the figure, reference numerals 1 to 15 are the same as those of the first embodiment shown in FIG. 1 and detailed description is omitted, but the characteristic portions of the second embodiment are the parts indicated by reference numerals 16, 17, and 18. ,Less than,
These parts will be described in detail.

In FIG. 4, reference numeral 16 denotes a coal feed pipe, which is provided so as to be movable in a vertical direction. Reference numeral 17 denotes a movable cylinder, which is coaxially close to the cylindrical portion 13 or slidably contacts. Reference numeral 18 denotes a support bar, one end of which is fixed to the coal feed pipe 16 and the other end of which holds a movable cylinder 17. Therefore, by moving the coal feed pipe 16 up and down, the movable cylinder 17 fixed thereto can be moved up and down, and the upper end position of the cylinder 13 of the inner hopper is moved up and down substantially.

In the vertical mill for coarse particles according to the second embodiment as described above, as shown in FIG. 5, when the coal feeding pipe 16 is lowered to lower the movable cylinder 17, and the upper end of the inner hopper is substantially lowered. As in the second embodiment shown in FIG. 2, the flow of the coarse particles repeatedly collides with and repels 30, 31, 32, and 33 on each side surface, and collides and repels with the coal feed pipe 34, and is collected in the inner hopper. However, some of the coarse particles repelled by the coal feed pipe 34 do not enter the inner hopper because the movable cylinder 17 is lowered, and collide with the outer hopper. The outer hopper stalls due to the collision, and the annular portions 20, 21 and
The hot air rising from 2 is carried to the mill exit as shown by the dotted line.

In the second embodiment described above, by lowering the coal feed pipe 16, the proportion of fine particles reaching the mill outlet pipe 2 increases, so that the classified particle size of the coal supplied to the boiler is increased and changed. The particle size can be adjusted to 3 mm or more according to the requirements of the boiler. In the first embodiment, the means for adjusting the particle diameter is not provided, but in the second embodiment, the particle diameter can be adjusted, and the needs of the boiler can be more finely answered. it can.

[0024]

As described above, the present invention has a coal feed pipe and an outer pipe arranged axially symmetrically with the coal feed pipe. In a vertical mill for coarse particles, which carries hot air to the mill outlet pipe at the upper part of the outer pipe; the outer pipe has a cylindrical shape in which the upper part and the lower part are larger than the central part, each of which is connected to the central part by a conical part, A mill outlet pipe is provided on the upper ceiling plate, and an outer cylinder vessel is provided at the lower part where the rotating bowl and rollers are arranged; and inside the outer cylinder vessel, the coaxial feed pipe and the central axis are arranged at a predetermined interval. And an inner cylinder hopper whose upper and lower parts are opened and whose lower part extends to the coal feed pipe outlet end. In this configuration, a structure in which a movable cylinder is provided in an upper outer cylinder of the inner cylinder hopper is also provided. Therefore, the following effects are obtained.

(1) Particles having a large particle diameter of about 3 mm or more are collected in an inner cylinder hopper, dropped on a rotary bowl, and re-ground with raw coal from a coal feed pipe, whereby only fine particles of 3 mm or less are boiled. Can be supplied to

(2) Only fine particles having a small particle diameter of less than 3 mm can be sent together with an airflow to a mill outlet tube and supplied as fuel to a boiler by pneumatic transportation.

(3) By lowering the movable cylinder of the inner cylinder hopper, the amount of fine particles carried to the mill outlet tube is increased, and the particle size is adjusted. Can supply this.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a vertical mill for coarse particles according to a first embodiment of the present invention.

FIG. 2 is a view showing a locus of coarse particles of a vertical mill for coarse particles according to the first embodiment of the present invention.

FIG. 3 is a view showing a trajectory of fine particles of a vertical mill for coarse particles according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a vertical mill for coarse particles according to a second embodiment of the present invention.

FIG. 5 is a view showing a locus of coarse particles of a vertical mill for coarse particles according to a second embodiment of the present invention.

FIG. 6 is a sectional view taken along line AA in FIG. 4;

FIG. 7 is a sectional view showing a configuration of a conventional vertical mill for coarse particles.

FIG. 8 is a diagram showing particles and gas flows in a conventional vertical mill for coarse particles.

[Explanation of symbols]

 1,16 Coal supply pipe 2 Mill outlet pipe 3,11,14 Conical part 4 Cylindrical part 5 Wind box 6 Rotary bawl 7 Drive part 8 Roller 9 Hot air blowing ring part 10,13 Cylindrical part 12,15 Lower discharge pipe 17 Movable cylinder Part 18 Support bar 40 Coarse grain 41 Fine grain

Continuation of front page (72) Inventor Yoshihisa Arakawa 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Sanishi Heavy Industries, Ltd.

Claims (2)

[Claims] 1. A coal supply pipe for supplying raw coal from an upper part, and an outer pipe which covers the periphery of an outlet part of the coal supply pipe, is arranged axially symmetrically with the coal supply pipe, and has an upper part connected to a mill outlet pipe, A vertical mill for coarse particles in which the raw coal supplied from the coal feed pipe is pulverized by a rotary bowl and a roller provided at the bottom in the outer pipe and the pulverized material is conveyed to the mill outlet pipe by hot air blown from the periphery; The outer tube has a cylindrical shape with the upper and lower parts larger than the central part, each connected to the same central part with a conical part, a mill outlet pipe is provided on the upper ceiling plate, and a rotating bowl and rollers are arranged at the lower part An outer cylinder container which is disposed inside the outer cylinder container at the same interval as the coal feed pipe at the same center axis as the coal feed pipe, with the upper and lower parts opened and the lower part extended to the coal feed pipe outlet end. A vertical mill for coarse particles, comprising a cylindrical hopper. 2. A movable cylinder which is disposed coaxially close to or in contact with the upper outer periphery of the inner cylinder hopper, is supported by the coal feed pipe, and is movable up and down together with the coal feed pipe. The vertical mill for coarse particles according to claim 1.