JPH0483541A - Method for stopping coal mill - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a method for shutting down a coal mill.

"Prior Art" FIG. 2 shows an example of the structure of a vertical coal mill that supplies pulverized coal to a coal-fired boiler or the like.

In FIG. 2, reference numeral 1 is a casing, 2 is a crushing motor, 3 is a table, 4 is a groove, 5 is a roller, 6 is a crusher, 7 is raw coal, 8 is a bunker, 9 is a conveyance motor, and IO is Conveyor, 11 is a coal feeder, 12 is a raw coal inlet pipe, 13 is a classification motor, 14 is a rotating cylinder, 15 is a blade, 16 is a rotary classifier, 17 is a hot air duct, 18 is an actuator, 19 is a throttle valve, 20 is a pulverized coal pipe, 21 is a control device, and 22 is a bearing.

The coal mill is operated by operating the conveyor motor 9, classification motor 13, and actuator 18 according to commands from the control device 21, and adjusting the driving speed of the conveyor 10, the rotation speed of the rotary classifier 16, and the opening degree of the throttle valve I9. be done.

Then, by the operation of the coal feeder 11, the raw coal 7 in the bunker 8 passes through the conveyor 10 and the raw coal inlet pipe 12, falls onto the rotating table 3, is crushed by the grooves 4 and the rollers 5, and is pulverized. The coal becomes coarse powder, is dried by hot air blown from the hot air duct 17, and is blown up inside the casing 1.

By appropriately setting the rotation speed of the rotary classifier 16, only pulverized coal passes between the blades I5 and is discharged from the pulverized coal pipe 20 as shown by the arrow in FIG. It is sent to a coal-fired boiler, etc. And feather 15
The coarse coal that has not passed through the cracks falls onto the table 3 again and is crushed again, as shown by the arrow in FIG. 1, and the process of blowing up with hot air and the like is repeated.

For example, multiple coal mills are often installed for one coal-fired boiler, and one way to change the output of a coal-fired boiler is to increase or decrease the number of connected coal mills. things will be done.

When stopping the coal mill, as shown by the broken line in Fig. 2, the stop signal from the control device 2 is sent to the crushing motor 2.
, conveyance motor 9, classification motor 3, actuator 18
By transmitting the information to the above, it brings them to a halt state.

"Problem to be solved by the invention" However, the crusher 6, the coal feeder 11, the rotary classifier 1
If the casing 6 is stopped immediately, a large amount of coal will remain in the casing 1, which is not desirable from a safety standpoint.

On the other hand, for example, when the coal feeder 11 is first stopped, the coal remaining in the casing 1 is pulverized, coarse coal and pulverized coal are blown up by hot air supply, and pulverized coal is extracted by classification. By repeating this process, the coal inside the casing 1 can be gradually discharged and the remaining amount can be reduced to 0. However, it takes a long time to discharge the coal inside the casing 1, and the above-mentioned coal-fired boiler This will prolong the output change time.

The present invention was made in view of the above circumstances, and aims to shorten the time required to stop the mill while ensuring safety.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention crushes raw coal supplied into a casing with a mill roller, and converts the crushed coal grains into coarse coal and fine powder with a rotary classifier. This is a stopping method applied to coal mills that discharge pulverized coal and return coarse pulverized coal to the mill rollers after being classified into charcoal and charcoal, and is a process of stopping the supply of raw coal into the casing by the coal feeder. and a step of gradually lowering the rotation speed of the rotary classifier to stop the rotary classifier as the raw coal supply starts to stop, and a step of removing coarse and pulverized coal from the rotary classifier when the rotary classifier decelerates The method for stopping a coal mill includes the step of extracting mixed coal particles and reducing the amount of residual coal in the casing to zero.

"Function J. During the operation of a coal mill, the raw coal supplied from the coal feeder,
Coarse coal particles and mixed coal grains of pulverized coal are in a quantitatively balanced state, and inside the casing, an appropriate amount of coal is accommodated with fluidity, and the coal feeder is The raw coal that passes through here is also stored inside.

Therefore, when the coal feeder is stopped, the raw coal stored downstream of the point where the movement of the raw coal is stopped is temporarily supplied into the casing and dropped into the casing. On the other hand, as the mill roller continues to pulverize the coal within the casing, the pulverized coal grains are sequentially fed into the rotary classifier.

In this case, when the rotational speed of the rotary classifier decreases, coarse coal becomes easier to pass through the rotary classifier as the rotational speed decreases, and all the mixed coal particles of coarse and pulverized coal in the casing become The amount of remaining coal in the casing is quickly brought to zero, and the overall downtime can be shortened.

"Example" Hereinafter, an example of the method for stopping a coal mill according to the present invention will be described with reference to FIGS. 1 and 2.

This embodiment is applied to the coal mill shown in FIG. 2, and the normal operation of the coal mill, that is, the raw coal 7 supplied inside the casing 1 is pulverized by the mill rollers 5, and the pulverized coal 7 is pulverized by the mill roller 5. After the coal grains are classified into coarse coal and pulverized coal by the rotary classifier 16, only the pulverized coal is discharged from the pulverized coal pipe 2o, and the coarse coal is returned to the mill rollers 5. The coal mill will be shut down if the situation arises.

Hereinafter, the method for bringing the coal mill to a stopped state will be explained step by step.

Normal state> In FIG. 1, as shown by to, the coal feeder 11 is pulverizing #! Constant supply of raw coal to 6 and rotary classifier 1
When the classification by the pulverizer 6, the pulverization of the coal by the pulverizer 6, and the hot air supply from the hot air duct 17 are performed, a state in which pulverized coal is discharged from the pulverized coal pipe 20 in fixed amounts continues.

<Stopping the coal feeder> In FIG. 1, as indicated by tl to t, the bunker 8 is stopped by a command signal from the control device 21 shown in FIG.
The movement of the raw coal 7 from the coal to the conveyor 10 is stopped by, for example, closing the coal gate.

The raw coal 7 stored downstream from the point where the movement of the raw coal 7 is stopped, that is, the raw coal left on the conhair 10 in the coal feeder 11 or in the raw coal inlet pipe 12 when the movement is stopped. Although coal 7 is dropped into the casing 1 due to the continued operation of the conveyor 10 for a while, the amount of coal fed quickly decreases as the coal is dropped, and reaches 0 at t.

Reducing the rotational speed of the rotary classifier> In FIG. 1, as indicated by t to t3, when the coal feeder 11 starts to stop, the rotational speed of the rotary classifier 16 is gradually reduced. When the rotary classifier 16 is normally operated, only pulverized coal is extracted from the pulverized coal pipe 20 by classification, but when the rotation speed of the rotary classifier 16 decreases, Coarse powder coal can easily pass through the blades 15 of the rotary classifier 16. therefore,
After t1, mixed coal grains of coarse pulverized coal and pulverized coal are discharged via the pulverized coal pipe 20, and as the rotation speed of the rotary classifier 16 decreases, the coal output rate of coarse pulverized coal decreases. Rise.

This trend shows that even if the rotary classifier 16 is completely stopped, hot air continues to be supplied while the crusher 6 is operating, and the amount of residual coal inside the casing 1 is quickly reduced to zero. You will be guided by In addition, in order to smoothly discharge coal downstream of the pulverized coal pipe 20, the rotary classifier 16 is set to be stopped after the amount of raw coal supplied to the inside of the casing 1 is reduced to zero.

<Mill rollers and hot air supply> As shown by [I to [,] in Fig. 1, the crusher 6
The operation stoppage and hot air supply stop are set to be delayed from the stop time of the coal feeder 11 and the stop time of the rotary classifier 16. As shown by t4 in FIG. 1, after coal is discharged from the pulverizer 6 and the remaining amount becomes 0, the operation of the crusher 6 and the supply of hot air from the hot air duct 17 are stopped. That is.

By such a process, when the coal mill is stopped, no coal grains are left inside the casing l, ensuring safety, and in addition, as shown in FIG.
The removal time of coal grains indicated by tl to t3 is shortened, and the output change time of the coal-fired boiler can be shortened.
Moreover, the time T shown in FIG. 1 required to stop the entire coal mill can be shortened.

"Effects of the Invention" According to the method for stopping a coal mill according to the present invention, the following effects are achieved.

(1) Since the raw coal supply into the casing is avoided and the rotational speed of the rotary classifier is gradually lowered, as the rotational speed decreases, coal removal from the coarse coal remaining in the casing is promoted. As a result, the amount of residual coal in the casing is brought to zero, and safety can be ensured.

(2) Coarse pulverized coal is discharged together with pulverized coal, which shortens the time required to remove coal grains from the casing, making it possible to quickly respond to coal mill shutdowns due to changes in coal-fired boiler output, etc. .

[Brief explanation of drawings]

Fig. 1 is a time chart showing an example of the method for stopping a coal mill according to the present invention, and Fig. 2 shows an example of the conventional structure of a vertical coal mill that supplies pulverized coal to a coal-fired boiler, etc. . l...Casing, 2...Crushing motor, 3...Table, 4...Concave groove, 5...
...Mill roller (roller), 6...Crusher, 7...Raw coal, 8.Old...Banka, 9...
・Transport motor, 10... Conveyor, 11...
... Coal feeder, 12 ... Raw coal inlet pipe, 13 ...
...Classifying motor, 14...Rotating tube, 15...
...Blade, 16...Rotary classifier, 17...
Hot air duct, 18... Actuator, 19...
- Throttle valve, 20...pulverized coal pipe, 21...control device, 22...bearing. Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Figure 1

Claims (1)

[Claims] The raw coal supplied into the casing is pulverized by a mill roller, and the pulverized coal grains are classified into coarse powder coal and pulverized coal by a rotary classifier, and then the pulverized coal is discharged and the coarse powder is returned to the mill rollers. This method involves stopping the supply of raw coal into the casing by the coal feeder, and gradually lowering the rotation speed of the rotary classifier as soon as the supply of raw coal starts to be stopped. The method includes a step of stopping the rotary classifier, and a step of bringing out mixed coal particles of coarse coal and pulverized coal from the rotary classifier when the rotary classifier decelerates to bring the amount of residual coal in the casing to zero. A method for stopping a coal mill, characterized by: