JP2001224972A - Mill purging method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mill purging method and device which are capable of executing optimum purging without excess and deficiency at all times even with coal varying in pulverizability and are capable of averting adverse influences to a mill itself, auxiliary facilities and a control system, etc. SOLUTION: The shortest purging time for the coal having the good pulverizability and the longest purging time for the coal having the poor pulverizability are previously set. At the point of the time the change rate of a mill differential pressure 37 falls down to a regulated value or below within a range from the shortest purging time to the longest purging time after the stop of a coaling machine 34, a stop signal 40 is outputted to a drive assembly 3 of a vertical mill 1 to stop the vertical mill 1, by which the mill purging is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method and apparatus for mill purging.

[0002]

2. Description of the Related Art Generally, a vertical mill 1 as shown in FIG. 2 has been used to pulverize a granular material such as coal supplied to a coal-fired boiler to obtain fine powder such as pulverized coal. I have.

A table 5 driven by a driving device 3 such as a motor through a speed reducer 4 is disposed in a lower portion of the casing 2 of the vertical mill 1. , A pivot bracket 6 is disposed so as to be tiltable about a horizontal shaft 7 supported on the journal cover 2 a of the casing 2, and a roller 8 is provided at a tip end of the pivot bracket 6 in a direction substantially orthogonal to the horizontal shaft 7. A fluid pressure cylinder 9 using a fluid such as oil is attached to the journal cover 2a of the casing 2, and the rod 9a of the fluid pressure cylinder 9 is extended. By pressing the pressing portion 6a of the pivot bracket 6 via the plunger 11 inserted into the plunger housing 10, the roller 8 is rotated horizontally. Pressed against the table 5 top you are, to cooperate with the roller 8 and the table 5, and is able to crushed granules of coal and the like on the table 5.

In the casing 2, an annular body 12 is disposed so as to surround the table 5, and the annular body 12 has
An air port 14 is provided so that the primary air 13 introduced into the casing 2 from a position below the table 5 of the casing 2 can be blown into the upper portion of the casing 2.

A head frame 15 is provided outside the upper portion of the casing 2 so as to communicate with the inside of the casing 2, and a bearing tube 16 is fixed in the head frame 15 so as to extend vertically. Bearings 17 and 18 are fitted into the bearing cylinder 16 at a required interval vertically.
A fine powder supply pipe 19 for supplying fine powder such as pulverized coal to a burner (not shown) of the boiler is connected to a side portion of the head frame 15.

A hollow cylindrical rotary shaft 20 extending vertically is fitted into the bearings 17 and 18, and a rotary classifier 21 is mounted on a portion of the rotary shaft 20 extending into the casing 2.
A pulley 22 is fitted to a portion of the rotary shaft 20 extending above the bearing tube 16.
A pulley 25 is fitted to an output shaft 24 of a driving device 23 such as a vertical motor installed outside the upper portion of the casing 2. The pulley 25 is fitted to the pulley 22 fitted to the rotary shaft 20. An endless belt 26 is looped between them.

In the rotary classifier 21, a rotary plate 27 is fitted to the lower end of the rotary shaft 20, and an outer peripheral portion of the rotary plate 27 is
It has a configuration in which a number of flat blades 28 extending upward are arranged.

A rotary classifier 2 is provided in the casing 2.
1, a truncated inverted conical reject chute 31 is provided.
A slit 32 extending along the inclined surface is formed in the first inclined surface so that a powder obtained by pulverizing a granular material such as coal blown up by the primary air 13 can pass through.

A chute 3 of a coal feeder 34 driven by a driving device 33 such as a motor is provided inside the rotary shaft 20.
A chute tube 30 whose upper end is connected to 5 is arranged so that its lower end is opened slightly above the roller 8 in the casing 2.

In FIG. 2, reference numeral 36 denotes a coal bunker for storing coal.

In the vertical mill 1 shown in FIG. 2, the granular material such as coal cut out from the coal bunker 36 to the coal feeder 34 is driven by the driving device 33 of the coal feeder 34 from the chute 35 to the chute pipe 30. The table 5 is dropped into the casing 5 through the, falls on the table 5, is driven by the drive unit 3 via the speed reducer 4, and contacts the table 5 rotating in the horizontal direction and rotates by contact with the table 5. Roller 8
The powder such as coal, which has been pulverized in cooperation with the above, rises in the casing 2 as shown by the arrow, accompanied by the primary air 13 blown out from the air port 14, and passes through the slit 32 of the reject chute 31. , Is blown up above the reject chute 31,
The coarse powder is classified by the rotary classifier 21 which is driven by the rotary shaft 20 and rotates together with the rotating shaft 20, and the fine powder such as the pulverized coal which has been classified into the coarse powder enters the head frame 15 through the rotary classifier 21. The coarse powder that has been sent from the head frame 15 to the fine powder feed pipe 19 and sent to a burner (not shown) of the boiler and that has been classified by the rotary classifier 21 slides down the reject chute 31. To be returned to the table 5.

When the load is reduced or when an abnormality occurs in the vertical mill 1, the coal feeder 34 and the vertical mill 1 may be stopped, but the vertical mill 1 is simply stopped. If the coal is left as it is, the coal remaining in the vertical mill 1 may ignite. Therefore, after stopping the coal feeder 34, the coal remaining in the vertical mill 1 is discharged. It is necessary to perform a so-called mill purge.

For this reason, conventionally, after the coal feeder 34 is stopped, a vertical mill 1 is set for a certain time by setting a timer.
, And then the driving device 3 of the vertical mill 1 is stopped.

[0014]

However, in the conventional case, the mill purge is performed simply by setting the timer regardless of the type of coal used. Therefore, in the case of coal having good pulverizability, the mill purge is completed early and the time of the timer is increased. In the meantime, the mechanical vibration due to the mechanical contact of the roller 8 with the table 5 continues, and the life consumption caused by the vibration of the incidental equipment is advanced or the mechanical damage is caused. Becomes incomplete, a large amount of coal remains in the vertical mill 1, the problem of ignition of coal still remains, and disturbance to the control system due to coal extraction when the vertical mill 1 is restarted also leads to. Had the disadvantage that

The present invention has been made in view of the above circumstances, and it is possible to always carry out an optimal purge of coal having different pulverizabilities without excess and deficiency, and to avoid a bad influence on a mill itself, ancillary equipment, a control system and the like. It is intended to provide a method and apparatus.

[0016]

SUMMARY OF THE INVENTION The present invention relates to a mill purging method for discharging coal remaining in a mill after stopping a coal feeder. The longest purge time is set in advance, and after the coal feeder is stopped, the mill is stopped when the change rate of the mill differential pressure falls within a range from the shortest purge time to the longest purge time and the mill differential pressure is equal to or less than a specified value. And a mill purging method.

Further, the present invention provides a mill purging apparatus for discharging coal remaining in a mill after stopping a coal feeder,
Mill differential pressure detector to detect the mill differential pressure, the shortest purge time in coal with good pulverizability, the longest purge time in coal with poor pulverizability are preset, and after the coal feeder stop signal is input, A controller that outputs a stop signal to the mill driving device when the change rate of the mill differential pressure detected by the mill differential pressure detector falls within a specified value within the range from the shortest purge time to the longest purge time. And a mill purge device comprising:

According to the above means, the following effects can be obtained.

In the mill purge method of the present invention, the shortest purge time for coal having good pulverizability and the longest purge time for coal having poor pulverizability are set in advance, and after the coal feeder is stopped, the shortest purge time is set to the longest. The mill purge is completed by stopping the mill within the range up to the purge time and when the rate of change of the mill differential pressure becomes equal to or less than the specified value.

Further, in the mill purge device of the present invention,
After the feeder stop signal is input to the controller, the mill differential pressure detected by the mill differential pressure detector within the range from the shortest purge time for coal with good pulverizability to the longest purge time for coal with poor pulverizability. When the pressure change rate becomes equal to or less than the specified value, a stop signal is output to the driving device of the mill, the mill is stopped, and the mill purge is completed.

As a result, in the method and apparatus for mill purging of the present invention, unlike the conventional method, mill purging is performed simply by setting a timer regardless of the type of coal used. It is performed, mechanical vibration due to the mechanical contact of the roller with the table continues, while the life consumption due to the vibration of the incidental equipment is advanced, or while there is no fear of causing mechanical damage,
In the case of coal with poor pulverizability, mill purge is incomplete, a large amount of coal remains in the vertical mill, the problem of coal ignition still remains, or the control system caused by coal output when restarting the vertical mill There is no need to worry about external disturbances.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention. In FIG. 1, the portions denoted by the same reference numerals as those in FIG. 2 represent the same components, and the mill purge remains in the vertical mill 1. When the coal is discharged from the system and the mill purge is completed, the coal in the vertical mill 1 almost disappears, and the thickness of the coal seam on the table 5 approaches zero. In order to mean that the change hardly occurs, in consideration of this, the mill differential pressure detector 38 for detecting the mill differential pressure 37, the shortest purge time (eg, 5 [min]) for coal having good pulverizability, The longest purge time (for example, 12 [min]) of coal having poor pulverizability is preset, and after the coal feeder stop signal 39 is input, the maximum purge time is within the range from the shortest purge time to the longest purge time and the mill difference is set. Pressure detector 38 Detected change rate specified value mill differential pressure 37 (e.g., 10 [mmAq / min]) as they become less, stop signal 4 to a vertical mill 1 of the driving device 3
And a controller 41 for outputting 0.

When the coal feeder stop signal 39 is input and the coal feeder stop signal 39 changes from "0" to "1", the controller 41 sets a predetermined time delay (having good grindability). An on-delay timer 43 that outputs a delay signal that changes to “1” as a shortest purge time elapse signal 42 by causing a time delay corresponding to the shortest purge time in coal).
The coal feeder stop signal 39 is input, and the coal feeder stop signal 39
Changes from "0" to "1", a predetermined time delay (a time delay corresponding to the longest purge time in coal having poor pulverizability) is caused, and the delay signal that changes to "1" is purged the longest. An on-delay timer 45, which is output as a time lapse signal 44, and a change in the mill differential pressure 37 detected by the mill differential pressure detector 38 are made to follow a change in the mill differential pressure 37 with a preset time delay. A first-order delay unit 47 that outputs a mill differential pressure signal 46 by cutting the small fluctuations of the above, and when the mill differential pressure signal 46 output from the first-order delay unit 47 changes, the rate of change is set to a set value or less. A process for limiting the value within the range is performed, and the mill differential pressure correction value 48
, A mill differential pressure correction value 48 output from the change rate limiter 49 and the primary delay
Subtractor 51 for obtaining a difference from the mill differential pressure signal 46 output from the microcomputer 51 and outputting a mill differential pressure change rate 50;
The signal monitor switch 5 that outputs the signal 52 of “1” when the mill differential pressure change rate 50 output from 1 becomes a specified value (for example, 10 [mmAq / min]) or less.
3 and a signal 52 output from the signal monitor switch 53, and when the signal 52 changes from “0” to “1”, a predetermined time delay (for example, 20
[Sec]), an on-delay timer 55 that outputs a delay signal that changes to “1” as a signal 54 that is equal to or less than a mill differential pressure change rate prescribed value,
An AND circuit 57 to which the shortest purge time elapse signal 42 output from the control signal 3 and the signal 54 below the mill differential pressure change rate prescribed value output from the on-delay timer 55 are input and outputs a logical product signal 56 thereof; The AND circuit 57
And the longest purge time elapsed signal 44 output from the on-delay timer 45 are input, and the logical sum signal of them is output as the stop signal 40 to the driving device 3 of the vertical mill 1. An OR circuit 58 is provided.

Next, the operation of the above illustrated example will be described.

The coal feeder 34 is stopped and the coal feeder stop signal 39
Is input to the controller 41, the on-delay timer 43 and the on-delay timer 45 of the controller 41 start counting.

At the same time, the mill differential pressure 37 is detected by the mill differential pressure detector 38 and input to the controller 41, where
In the first-order delay device 47, the mill differential pressure detector 38
By following the fluctuation of the mill differential pressure 37 detected in the above so that a preset time delay occurs, the minute fluctuation of the mill differential pressure 37 is cut, and the mill differential pressure signal 46 is changed by the change rate limiter 49 and When the mill differential pressure signal 46 output from the primary delay unit 47 changes, the rate of change is limited to a set value or less. The mill differential pressure correction value 48 is output to the subtractor 51, where the mill differential pressure correction value 48 output from the rate-of-change limiter 49 and the mill output from the primary delay unit 47 are output. The difference from the differential pressure signal 46 is obtained, and the mill differential pressure change rate 50 is output to the signal monitor switch 53. In the signal monitor switch 53, the mill differential pressure change rate output from the subtractor 51 is output. 50 is a specified value (e.g., 10 [m
mAq / min]), the signal 5 of “1”
2 is output to an on-delay timer 55, and the signal monitor switch 5
3 changes from “0” to “1” when the signal 52 output from the “3” changes from “0” to “1” (for example, 20 [sec]
c]) and the delay signal that changes to “1” is converted to a signal 54 that is equal to or less than the mill differential pressure change rate prescribed value as an AND circuit 57.
Output to

The AND circuit 57 has a shortest purge time elapse signal 42 output from the on-delay timer 43.
Both the shortest purge time elapsed signal 42 and the signal 54 below the mill differential pressure change rate prescribed value output from the on-delay timer 55 are "1", that is, after the coal feeder 34 is stopped, When the time corresponding to the shortest purge time has elapsed in the coal having good properties and the rate of change of the mill differential pressure 37 has fallen below a specified value, the AND signal 56
Is output to the OR circuit 58 as “1”, and the OR circuit 5
8 outputs a stop signal 40 to the drive unit 3 of the vertical mill 1, the drive unit 3 of the vertical mill 1 stops, and the mill purge is completed.

Here, if the AND signal 56 output from the AND circuit 57 does not become "1", the mill differential pressure 3
7 is not less than the specified value, the longest purge time elapse signal 44 is "1", that is, the longest purge time elapses in coal with poor pulverizability after the coal feeder 34 is stopped. Then, the stop signal 40 is output from the OR circuit 58 to the driving device 3 of the vertical mill 1, the driving device 3 of the vertical mill 1 is stopped, and the mill purge is completed.

As a result, unlike the conventional case where the mill purge is simply performed by setting the timer regardless of the used coal, the mill purge is excessively performed on the coal having good pulverizability, and Mechanical vibration due to mechanical contact continues, and there is no fear that the life consumption due to the vibration of the incidental equipment will advance or cause mechanical damage. A large amount of coal remains in 1, and there is no fear that the problem of ignition of coal still remains, or disturbance to the control system due to coal extraction when the vertical mill 1 is restarted.

In this way, the optimum purge can always be carried out even for coals having different pulverizabilities without excess and deficiency, and adverse effects on the mill itself, incidental facilities, control systems and the like can be avoided.

The mill purge method and apparatus according to the present invention include:
It is needless to say that the present invention is not limited to the illustrated example described above, and various changes can be made without departing from the scope of the present invention.

[0033]

As described above, according to the mill purging method and apparatus of the present invention, it is possible to always carry out the optimum purging even for coals having different pulverizabilities without excess and deficiency. And the like, which can avoid an adverse effect on the operation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 vertical mill (mill) 3 driving device 34 coal feeder 37 mill differential pressure 38 mill differential pressure detector 39 coal feeder stop signal 40 stop signal 41 controller 42 shortest purge time elapsed signal 44 longest purge time elapsed signal 50 mil Differential pressure change rate 54 Mil Differential pressure change rate specified value or less signal

Claims (2)

[Claims] In a mill purging method for discharging coal remaining in a mill after stopping a coal feeder, a shortest purge time for coal having good crushability and a longest purge time for coal having poor crushability are preset. In addition, after the coal feeder is stopped, the mill purging method is characterized in that the mill is stopped within a range from the shortest purge time to the longest purge time and when the rate of change of the mill differential pressure becomes equal to or less than a specified value. . 2. A mill purge device for discharging coal remaining in a mill after stopping a coal feeder, a mill differential pressure detector for detecting a mill differential pressure, a shortest purge time for coal having good pulverizability, The longest purge time for coal with poor pulverizability is set in advance, and after a coal feeder stop signal is input, the mill differential pressure detected within the range from the shortest purge time to the longest purge time and detected by the mill differential pressure detector And a controller for outputting a stop signal to the mill driving device when the pressure change rate becomes equal to or less than a specified value.