JPH0483542A - Method for stopping coal mill - Google Patents

Abstract

PURPOSE:To accurately secure the feed amount of coal at the stop time of a coal mill while securing safety by performing operation stopping a coal feeder by the stop command of the coal mill and adding attenuation level data to the unit time level data of the coal feed amount signal of the coal feeder to continuously perform output at the stop time of the coal feeder. CONSTITUTION:When the steady supply of raw coal to a grinder 6 by a coal feeder 6, the classification due to a rotary classifier 16, the girding of coal due to the grinder 6 and the supply of hot air from a hot air duct 17 are carried out, coal feed amount data is transmitted to a coal fired boiler. A coal gate 23 is closed by the command signal from a control apparatus 21. When raw coal 7 is not fed to a conveyor 10 and the coal feeder 11 is stopped, the raw coal 7 left on the conveyor 10 or in a raw coal inlet pipe 12 is allowed to fall in a casing 1 for a while from the starting time of stop by the continuous operation of the conveyor 10 or natural falling and the feed amount of coal is rapidly reduced with falling to become zero at t3. By this method, the output control of the coal fired boiler can be carried out with high accuracy.

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 l 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 10 is a Conveyor, 11 is a coal feeder, 12 is a raw coal inlet pipe, I3 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 a pulverized coal pipe, 21 a control device, 22 a bearing,
23 is a coal gate, and 24 is raw coal supply amount detection means.

The operation of a coal mill is as shown by the dashed arrow in Figure 2.
By issuing a command from the control device 21, the transport motor 9, the classification motor 13, and the actuator 18 are operated,
The driving speed of the conveyor 1G, the rotational speed of the rotary classifier 16, the opening degree of the throttle valve 19, etc. are adjusted. Then, by the operation of the coal feeder ii, the raw coal 7 in the bunker 8 falls onto the rotating table 3 via the conveyor 10 and the raw coal inlet pipe 12, and is crushed by the grooves 4 and rollers 5 to become 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 15 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. The coarse pulverized coal that could not pass between the blades 15 is as shown by the arrow in FIG.
It falls onto the table 3 again and is crushed again, and then the process of blowing up with hot air and the like is repeated.

Conventionally, it has been difficult to directly measure the amount of pulverized coal produced in a coal mill, so by establishing a steady equilibrium state, the amount of raw coal supplied per unit time and the amount of pulverized coal produced per unit time have been calculated. For example, the supply amount detection means 24 compares the load of the conveyor lO in the coal feeder 11 with the load of the conveyor lO.
The supply amount is calculated based on the transfer speed of the coal supply amount, and the coal feeding amount signal is obtained in place of the coal output amount signal.

On the other hand, 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 change the number of connected coal mills. Increases and decreases are performed. When stopping the coal mill, a stop signal from the control device 21 is transmitted to the crushing motor 2, conveyance motor 9, classification motor 13, actuator 18, and coal gate 23, as shown by the broken line in FIG. This leads them to a stopped state.

``Problem to be solved by the invention'' However, due to a command to stop the coal mill, the coal feeder 1
1, even after the conhair 10 is stopped, the coal remaining in the casing 1 will be pulverized, coarse coal and pulverized coal will be blown up by hot air supply, and pulverized coal will be classified by classification. Even if the actual amount of coal produced does not immediately become zero due to continuous coal production, and the amount of coal produced based on the supply amount is apparently 0, coal production will continue to be carried out. This will affect the output of the coal-fired boiler. And Coal Gate 23
Even if the conveyor 10 is set to a closed state and the conveyor 10 is set to a stopped state,
Since some of the raw coal on the conveyor 10 and the raw coal in the raw coal manifold tube 12 are dropped into the casing 1, the amount of coal accommodated in the casing 1 increases by that amount, and this increase This will also add up the error.

Furthermore, if the crusher 6 and the rotary classifier 16 are stopped immediately, the difference between the amount of coal supplied and the actual amount of coal produced will be eliminated, but a large amount of coal will remain in the casing 1, resulting in safety concerns. Undesirable.

The present invention has been made in view of the above circumstances, and aims to ensure accuracy in the amount of coal output when the coal mill is stopped while ensuring safety.

"Means for Solving the Problems" The present invention proposes three means for solving the above problems.

The first method consists of a coal feeder that feeds the raw coal in the bunker into the casing in fixed quantities, a crusher that crushes the supplied raw coal, and a pulverizer that classifies the coal grains blown up by the hot air sent into the casing. This applies to coal mills that are equipped with a rotary classifier that outputs pulverized coal using a coal feeder, and that obtains a coal feeding amount signal from a coal feeding machine as a coal output amount signal, and is used as a stop command for a coal mill. At the same time, the coal feeder is stopped by adding attenuation level data that gradually decreases from this unit time level data to the unit time level data of the coal feed amount signal immediately before the coal feeder starts to stop. The method for stopping a coal mill is such that the output continues when the coal machine is stopped.

The second means is configured to add to the attenuation level data, when the coal feeder is stopped, the amount of change in the level data corresponding to the amount of raw coal supplied into the case song until the coal feeder comes to a complete stop state is added to the attenuation level data. The method for stopping a coal mill is an addition to the first method.

The third means is a coal mill in which attenuation level data is given by the e-KX formula, and a configuration is added to the first means or the second means, where K is the reciprocal of the time constant and X is the elapsed time. This is the stopping method.

"Effect" In the first means, when the coal mill is in operation, the amount of raw coal supplied from the coal feeder becomes equal to the amount of pulverized coal output from the rotary classifier, A coal output amount signal is obtained in which the amount of coal fed is the amount of coal output.

When the coal feeder is stopped by the coal mill stop command,
Coal production using the coal remaining in the casing will continue for a while, but since the amount of coal stored in the casing is determined by the size of the casing, When the attenuation level data is added to the unit time level data of the coal feed amount signal as a coal storage amount signal of the casing and output, an output modeled of the remaining amount of coal output from the casing after the coal feeder stops is generated. A coal amount signal is obtained, the error with the actual amount of coal output is reduced, and it is possible to avoid affecting the output of the coal-fired boiler. Furthermore, by continuing to operate equipment such as a crusher that is involved in extracting coal from the casing for a while, no coal remains in the casing.

In the second means, when the coal feeder is stopped, correction is made for the raw coal supply that was interposed between the coal feeder and the casing.

In the third means, the attenuation level data is e-KX
By being given by a gentle curve in the equation, the modeled coal output signal approximates the rate of change in the coal output of pulverized coal from an actual coal mill, reducing the occurrence of errors. .

"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 is carried out in the normal operation of the coal mill, that is, raw coal 7 fed into the case song 1 is pulverized by the mill rollers 5. After the coal particles are classified into coarse coal and pulverized coal by the rotary classifier 16, only the pulverized coal is discharged from the pulverized coal pipe 20, 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, raw coal is constantly supplied to the crusher 6 by the coal feeder 11, and the rotary classifier 16
If the coal is classified by the pulverizer 6, the coal is pulverized by the pulverizer 6, and the hot air is supplied from the hot air duct 17, or based on the output adjustment command of the coal-fired boiler, the output (coal production amount) of the coal mill is adjusted. When the reduced operation is performed, the state in which pulverized coal is continuously discharged from the pulverized coal pipe 20 in fixed amounts, and the amount of coal fed and the amount of coal output are balanced, and the coal feeder The coal supply amount obtained by the supply amount detection means 24 of ii is replaced with the coal output amount, and the coal output amount data is transmitted to the coal-fired boiler.

<Call Gate> In FIG. 1, as indicated by t, the call gate 23 is closed in response to a command signal from the control device 21 shown in FIG. 2, for example. At the moment when the coal gate 23 is closed, there is raw coal directly below it, so that part of the raw coal is sent to the conveyor 10 for a short time, and the amount of coal fed is constant between tl and t. .

<Stopping the coal feeder> When the raw coal 7 is no longer fed to the conveyor 10 and the coal feeder ti is stopped, the top of the conveyor 10 and the raw coal inlet pipe 12 will be stopped for a short time after the start of the stop. The raw coal 7 left inside is dropped into the casing I due to continued operation of the conveyor IO and natural fall, but as the raw coal 7 is dropped into the casing I, the amount of fed coal rapidly decreases and reaches 0 at t3.

<Amount of coal output from the casing> The raw coal 7 is not fed into the inside of the casing 1,
Moreover, when the coal inside the casing l is discharged, the total amount of coal discharged matches the total amount of coal accumulated inside the casing. According to the research conducted by the present inventors, the amount of coal produced per hour tends to decrease as the amount of accumulated coal decreases.
It has been found that the change in the coal output signal in this case approximately draws a gentle attenuation curve that approximates the e-1 equation, as shown by the curve after t.

<Output of modeling signal> Based on the above knowledge, at the same time as coal feeder ii starts to stop,
Based on the unit time level data of the stable coal feeding amount signal immediately before the start of stopping of the coal feeding machine ii (immediately before tz), and
A modeling signal is created by adding attenuation level data having an attenuation curve that gradually decreases from this unit time level data, and this is used as a coal feeding amount signal at the time of stopping coal feeding III to a coal-fired boiler (not shown). transmission to automatic control.

As mentioned above, when the coal feed amount signal level per unit time is 1, the modeling signal is given by the e-KX formula, where e is the base of the natural logarithm, K is the reciprocal of the time constant T, and is the elapsed time.

The time constant T in this case is set by the amount of coal accumulated inside the casing l.

<Reducing the rotation speed of the rotary classifier> In Fig. 1, as shown at t4, the rotary classifier Lower the rotation speed to 16 and stop. When the rotary classifier 16 is in steady operation (1
1), pulverized coal is discharged from the pulverized coal pipe 20 by classification, but as the amount of coal inside the casing l decreases, the amount of pulverized coal particles blown up into the rotary classifier 16 decreases. In addition, as the rotational speed of the rotary classifier 16 decreases, the coal grains tend to pass through the blades 15 of the rotary classifier 4116 more easily, so the rotation is performed at an appropriate timing such as after a time constant T has elapsed from t. Even if the type classifier 16 is stopped, it will not have any effect.

Stopping the mill motor> After the time has elapsed for the amount of coal output to reach 0, as shown by L in Fig. 1, the grinding motor (mill motor) shown in Fig. 2 is stopped.
)2 is stopped.

<Stopping mill ventilation> After stopping the mill motor 2, all the coal grains slightly remaining inside the casing 1 are discharged, and then hot air supply (
In FIG. 1, the mill ventilation is brought to a stopped state as shown at t8.

Through such a process, when the coal mill is stopped, no coal grains are left inside the casing 1, ensuring safety. It is possible to output the amount of coal produced that is equivalent to the amount of accumulated coal, thereby ensuring the accuracy of the amount of coal produced.

"Effect of the invention" According to the method for stopping a coal mill according to the first invention, (1)
A modeled signal in which attenuation level data that gradually decreases from this unit time level data is added to the unit time level data of the coal feed amount signal immediately before the coal feeder starts to stop, is continuously output when the coal feeder stops. Therefore, safety can be ensured by crushing and discharging the coal accumulated in the casing.

(2) Even if the coal feeding amount signal is used as the coal output amount signal in a steady state, when the coal output amount signal disappears due to the stoppage of the coal feeder, the modeling signal will change to the accumulated coal inside the casing. This approximates the amount of coal output, which suppresses the occurrence of errors in the amount of coal output and avoids affecting the output of the coal-fired boiler.

(3) It is applicable even when the volumes of the casings are different, and is highly practical.

According to the method for stopping a coal mill according to the second invention, when a coal feeder is stopped, the amount of change in level data corresponds to the amount of raw coal supplied into the casing until the coal feeder reaches a complete stop state. is added to the attenuation level data in the first invention, so (1) and (2) in the first invention are added to the attenuation level data in the first invention.
) In addition to the effects of (3), there may be cases where there is raw coal between the coal feeder and the casing when the coal feeder is stopped, or the time it takes for the coal feeder to come to a complete stop. Even in the case where temporary coal feeding is performed during this time, the amount of raw coal supplied can be corrected to accurately determine the amount of coal produced when the coal mill is stopped.

According to the method for stopping a coal mill according to the third invention, in the first invention or the second invention, the attenuation level data is
Since the modeled signal is given by a gentle curve of the e-KX formula, in addition to the effects of the first or second invention, the coal output signal when the coal feeding machine etc. is stopped is The rate of change in the coal output amount of pulverized coal from the mill is approximated, and even when the coal mill is stopped, there are fewer errors in the coal output signal, making it possible to adjust the output of the coal-fired boiler to a higher level. It can be carried out with precision.

It has the following effects.

[Brief explanation of drawings]

Fig. 1 is a time chart showing an embodiment 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 (mill motor), 3-...Table, 4...Concave groove, 5
...-Mill roller (roller), 6...Crusher, 7...Raw coal, 8...Bunker, 9...Transport motor, lO, conveyor, 11...・・Coal feeder, 1
2...Raw coal inlet pipe, 13...Classifying motor, 1
4...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,
23... Coal gate, 24... Supply amount detection means. Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Agent Patent Attorney Masatake Shiga

Claims (1)

[Claims] i. A coal feeder that supplies raw coal in a bunker to a casing in fixed quantities, a pulverizer that crushes the supplied raw coal, and a coal grain blown up by hot air sent into the casing. In a coal mill that is equipped with a rotary classifier that classifies and outputs pulverized coal, and also obtains a coal feed amount signal from a coal feeder as a coal output amount signal, the coal feeder is activated by a stop command from the coal mill. At the same time as the operation to stop the coal feeder, the unit time level data of the coal feed amount signal immediately before the start of stopping the coal feeder is
A method for stopping a coal mill characterized by adding attenuation level data that gradually decreases from this unit time level data and continuously outputting the data when the coal feeder is stopped. ii. When the coal feeder is stopped, the amount of change in the level data corresponding to the amount of raw coal supplied into the casing until the coal feeder comes to a complete stop state is added to the attenuation level data. A method for shutting down a coal mill according to claim i. iii. The method for stopping a coal mill according to claim i or ii, wherein the attenuation level data is given by the e^-^K^X formula, K is the reciprocal of a time constant, and X is the elapsed time. .