JPH01203058A - Vertical mill - Google Patents

Abstract

PURPOSE:To prevent delayed crushing of coal to pieces in a vertical mill and avoid a delayed response due to the delayed crushing timing by providing a blow-up means which blows up coal held up in the vertical mill, in the casing of a classifier. CONSTITUTION:If a command for lifting a load is issued, a control drive 22 drives to set an operating plate (blow-up means) 15 in the casing 14 of a classifi er 6 in an open condition for a specified time well in advance. Then the separa tion performance of the classifier 6 is temporarily decreased by opening of the operating plate 15 to supply pulverized coal obtained by blowing operation of coal held up in the vertical mill 2 to a coal feeder pipe 13 precedently. Thus, the delay in coal crushing in the vertical mill 2 is eliminated by operating action of an operating means 15 and the vertical mill 2 is controlled satisfacto rily in response to a load.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vertical mill that supplies pulverized coal to, for example, a coal-fired boiler, and particularly improves the delay in response of pulverized coal to a coal conveyance pipe when the load increases. This invention relates to a vertical mill suitable for.

[Conventional technology]

With the increase in the number of nuclear power plants, the proportion of nuclear power plants used for pace road operation is increasing.

Therefore, thermal power plants are required to perform intermediate load operation for adjusting the supply and demand of electricity, and coal-fired power plants are also required to meet this requirement.

A vertical mill system for a coal-fired boiler consists of a coal supply system to the vertical mill, a vertical mill that pulverizes the coal, and a drive control system that controls the amount of coal and air supplied to the vertical mill and sends it to the burner. The system consists of a control system that adjusts the amount of pulverized coal supplied. Hereinafter, a conventional vertical mill system will be explained using FIG. 6.

The coal supply system includes a coal bunker 1 and a coal feeder 3 that supplies coal from the coal bunker 1 to a vertical mill 2. Further, the vertical W mill 2 is equipped with a crushing section consisting of a rotary table 4 and crushing rollers 5 at the lower part, and a classifier 6 for separating coarse powder at the upper part. Coal from the coal bunker 1 is transferred from the coal feeder 3 to the coal feed pipe 7 located in the center of the vertical mill 2.
The amount of coal is controlled by adjusting the rotational speed of the belt conveyor 8 of the coal feeder 3 using a motor 9. On the other hand, air is introduced into the vertical mill 2 from the air duct 10 through the annular throat 11 at the bottom of the vertical mill 2, and the amount of air is 1
It is controlled by adjusting the opening degree of the air damper 12 located at zero.

In such a vertical mill system, when a load increase command is given, coal feeding and air volume are controlled in advance to improve responsiveness, but there is a delay in the pulverization of coal in the vertical mill 2. Therefore, when the load increases from 50% to 100%, it takes about 15 minutes for pulverized coal to be output from the vertical mill 2 to the coal feed pipe 13 and to reach a steady state. For this reason, due to the delay in response of the vertical mill 2, current coal-fired power plants are operated at a load change rate of 1 to 2 inches/- when the load changes.

[Problem that the invention seeks to solve]

In conventional vertical mills, the supply amount of coal and air is controlled to increase in advance when a load increase command is issued, but the coal in the vertical mill is After being circulated, the coal is taken out as pulverized coal to the coal pipe, which has the disadvantage that it cannot fundamentally improve dead time and response delay when a load increase command is issued due to the delay in pulverization within the vertical mill.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vertical mill that eliminates the drawbacks of the prior art described above, eliminates the delay in pulverization of coal in the vertical mill, and allows good load response control.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a classifier with blow-up means for blowing up the coal held in the mill.

[Effect]

When a load increase command is issued, the separation performance of the classifier is temporarily lowered by the blow-up means attached to the classifier for a certain period of time, and the coal held in the mill is turned into pulverized coal and sent to the coal pipe in advance. Since it can be supplied, wasted time and response delay in vertical mills are improved.

〔Example〕

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

Figures 1 and 2 are enlarged vertical cross-sectional views of main parts according to embodiments of the present invention, Figure 3 is a schematic system diagram of a vertical mill system for coal-fired couplants, and Figure 4 is the classification efficiency of the classifier. A characteristic curve diagram of the entrainment ratio, and FIG. 5 is a control system diagram of the vertical mill system.

Hereinafter, the present invention will be explained in detail with reference to FIGS. 1 and 3, and numerals 1 to 13 indicate the same parts as in the conventional one.

In FIG. 3, the vertical mill system of a coal-fired power plant includes a coal supply system 100 to a vertical mill 2, and a burner (not shown) that supplies pulverized coal with air to a coal feeder 113 after pulverizing and classifying the coal. The control system 300 controls the amount of coal and air supplied to the vertical mill 2 to adjust the amount of pulverized coal supplied to the coal pipe 13. ing. The vertical mill 2 includes a crushing row 25 that crushes coal supplied by the coal feeder 3;
A classifier 6 is provided in which after separating the coarse powder from the coal to be pulverized, only the fine powder is increased along with the air from the coal feeding pipe 13.The casing 14 of the classifier 6 is equipped with a A blow-up means (opening/closing plate) 15 is provided.

Further, the control system 300 takes in information on the amount of coal supplied by the coal feeder 3 and the amount of air, and based on this information, drives and controls the vertical mill 2 in advance in response to a request for a change in the boiler load. The amount of pulverized coal supplied can be adjusted.

Here, the vertical mill 2 will be explained in more detail with reference to FIGS. 1 and 3.

The coal feeder 3 includes a rotation detector 16 that detects the speed of the belt conveyor 8 and a load cell 17 that measures the weight of coal on the belt conveyor 8, and feeds coal from the coal bunker 1 to the vertical mill 2. It is now available for supply.

The vertical q-mill 2 usually includes three crushing rollers 5 inside thereof, and these crushing rollers 5 are rotatably supported by a fixed shaft (not shown). Gear 18 is drive motor 1
The rotational force of 9 is decelerated and transmitted to the rotary table 20. In addition, as shown in FIG.
The blow-up means (opening/closing plate) 15 is connected to the lever mechanism 21, and when the driving force from the control drive 22 is transmitted to the lever mechanism 21, the blow-up means (opening/closing plate) Plate) 15 opens and closes.

Further, an air duct NO is connected to the bottom of the vertical mill 2, and the air duct IO includes an air supply means including an air damper 12, an orifice 23, and a damper control drive 24 for driving the air damper 12. is provided.

Coal from the coal bunker I is sent to a coal feeder 3, and the weight of the coal on a belt conveyor 8 provided in the coal feeder 3 is detected by a load cell 17. Further, the rotation speed of the belt conveyor 8 of the coal feeder 3 is detected by a rotation detector 16. By multiplying these coal weight signals and rotational speed signals by the calculator 25, the amount of coal fed can be detected.

On the other hand, coal from the coal feeder 3 is supplied onto the rotary table 20 via the coal feed pipe 7 located at the center of the vertical mill 2, and is simultaneously crushed as it passes between the crushing roller 5 and the rotary table 200 due to centrifugal force. and is sent to the upper throat 26.

This pulverized coal passes through the throat 11 to the vertical mill 2
It moves to the throat upper part 26 together with the air supplied therein, and is conveyed to the vane 27 of the classifier 6. At this time, coarse coal particles among the pulverized coal are separated from the airflow at the upper throat 26 and returned to the rotary table 20 for primary classification. In addition, the particles that have entered the classifier 6 are subjected to centrifugal force by the vanes 27 of the classifier 6, and relatively coarse particles are separated from the airflow by the centrifugal force, and are returned from the discharge port 28 located at the bottom of the classifier 6. It is returned onto the rotary table 20 and subjected to secondary classification. The pulverized coal that has been secondarily classified by the classifier 6 is sent together with air to a burner (not shown) via a coal feeder v13, and is then fed into a boiler and burned.

The coal thus supplied into the vertical mill 2 is circulated through the vertical mill 2 several times through primary classification and secondary classification.
It is extracted as pulverized coal. In addition, the air for conveying the pulverized coal is passed through a differential pressure detector 2 that detects the differential pressure in the orifice 23.
9 determines the amount of conveying air, and the damper control drive 24 controls the amount by adjusting the opening degree of the air damper 12.

By the way, conventional coal-fired couplants are operated for pace loads because the load response of the vertical mill 2 is slow, and the load change rate is about 1 inch/hill.

However, the demand for intermediate load operation is increasing for coal-fired couplants, and conventional operation at a load change rate cannot meet this demand.

Therefore, the present invention temporarily opens the blow-up means (opening/closing plate) 15 provided in the classifier 60 casing 14 when the load changes to remove the coal held in the vertical mill 2, that is, the coal circulating through primary classification and secondary classification. As a result, the separation performance of the classifier 6 is reduced, and thereby the coal held in the vertical mill 2 is carried out from the throat upper part 26 into the classifier 6, thereby compensating for the delay in pulverizing the coal. FIG. 4 shows an example of data on which the present invention is based. The vertical axis in FIG. 4 shows the separation efficiency of the classifier 6, that is, the proportion of particles that enter the classifier 6 that are separated (collected) by the classifier 6, and the horizontal axis shows the separation efficiency of the classifier 6.
It shows the proportion of the entering air that leaks through the blow-up means (opening/closing plate) 15. As is clear from FIG. 4, when the infiltration rate exceeds 3%, most of the particles entering the classifier 6 pass through the classifier 6 without being separated by the classifier 6.
It can be seen that the coal is sent to the coal feed pipe 13.

On the other hand, when a load change is requested, the control system 300 issues a command to the coal feeder 3 and drives the motor 9 to increase the coal feed t.
In addition, the control drive 24 of the air damper 12 gives an opening command to the air damper 12 so that the request can be met.

FIG. 5 is a schematic control system diagram of a control device used in an embodiment of the present invention. In FIG. 5, 30 is a total fuel detector, 31 is a first-order lag device, 32 is a subtracter, 33 is a multiplier, 3
4 is a proportional integral calculator, 35 is a multiplier, 36 is an adder, 3
7 is a bias setting device, 38 and 39 are automatic/manual switching devices, and the rotation speed of the motor 9 is set to g! 4 Adjust.

40 is a function generator, 41 is a bias generator, 42 is an adder, 43 is a subtracter, 44 is a signal controller, and 45 is an automatic manual switch, which opens and closes the air damper 12. 46 is an output demand signal, 47 is a differential calculator, 48 is a differential calculator, 4
9 is a signal limiter, 50 is a rate of change limiter, 51 is an adder,
52 is a multiplier, 53 is a signal switcher, 54 is an adder, 55
is a signal generator, 56 is a signal switch, 57 is an upper and lower limit limiter, 58 is a lower limit limiter, 59 is a signal generator, 60 is an automatic manual switch, and the blow-up means 15 is opened by the control drive 22 of the blow-up means 15; close In addition, 6
1 is an adder.

Next, control of the control device 300 will be explained. In response to the mill master command as a coal amount command value commensurate with the plant load, the total fuel of the amount of coal fed from the coal feeder 3 is detected by the total fuel detector 30, and the mill master command is pulverized until coal comes out. The subtracter 32 subtracts the value obtained by first-order delaying the time required for the first-order delay by the first-order lag detector 31 . After the gain correction based on the number of stitches of the vertical mill 20 in operation is applied to the deviation signal of the subtractor 32 using the multiplier 33, the proportional-integral adjuster 34
Calculate the proportional integral with , and operate the coal feeder 3 until the deviation disappears. The multiplier 35 performs calorie correction on the deviation signal from the proportional integrator 34, and this calorie-corrected command value is output as a coal feed amount command signal for each vertical mill 2 in operation. Become. These commands to each vertical mill 2 drive the motor 9 of the coal feeder 3 to limit the amount of coal and control the amount of air via the air damper 12. Bias setting device 37.41, when control is possible in each mil unit for coal feeder command and air command.
Adjust with adders 36 and 42. In addition, automatic manual switch 3
8, convert the amount of air to the amount of coal feed using the function generator 40,
This is an opening command for the air damper 12. With respect to this command value, the air flow rate is detected using the signal from the air differential pressure detector 29,
The deviation is taken and the subtractor 43 detects the deviation, and the proportional-integral regulator 44 controls the air damper 1 so that the deviation disappears.
Operate 2.

Now, load request value (output demand signal) during load change 4
6 is differentiated by a differential calculator 48 to create a fuel amount appropriate for the load change, and after limiting the variation width by an upper and lower limit limiter 49, the fuel system is adjusted by a combination of a change rate limiter 50 and an adder 51. Create signals, excess fuel commands/insufficient fuel signals, and determine the optimal rate of change and width of change. Multiply this signal! a
By performing gain correction based on the number of mills in step 52 and adding them, it is possible to control the amount of coal feeding and the amount of air in advance.

Further, the control system (opening/closing plate) 150 of the blowing means in the casing 14 of the classifier 6 is operated as follows.

First, during normal operation, the a side of the switch 56 is selected, and during load changes including startup and stop, the b side is selected.

During normal operation, the switch 56 selects the a side, and the signal generator 55 is set to the closed state.

According to the opening/closing signal of the signal generator 55 mentioned above, the classifier 61
Blow-up means (opening/closing plate) 15 in the casing 14 of
control drive 22. On the other hand, during the process of load change, the switch 56 selects the b side, and the output demand signal (load change request value) 46 is differentiated by the differentiator 47 to create a preceding signal with good response, and this signal On the other hand, the upper and lower limit controller 57 creates a signal that limits large changes.

Adder 6 adds the load change speed signal created as described above to the open signal from signal generator 55 as the speed signal during load change.
Add by 1. In response to this total signal, the control drive 22 of the blow-up means (opening/closing plate) 15 in the casing 14 of the classifier 6 is driven, and the blow-up means (opening/closing plate) 15 is preliminarily set to be open for a certain period of time.
The coal held in the vertical mill 2 is blown out into the coal feed pipe 13 by the blow-up means 15.

By operating in this way, it is possible to compensate for the crushing delay of the vertical mill 2.

In short, according to the embodiment of the present invention, the coal supplied by the coal feeder 3 is made into pulverized coal by the vertical mill 2, and the pulverized coal is conveyed by air and passed from the coal feeding pipe 13 through a burner (not shown). 1 vertical mill Z to feed the boiler
The blow-up means (opening/closing plate) 15 in the casing 14 of the classifier 6 installed in the classifier 6 is configured to be openable and closable, and information on the coal feed i and air waves is taken in, and based on this information, the The control device 300 that controls the drive of the vertical mill 2 in advance to adjust the fuel supply area controls the blow-up means (opening/closing plate ) 15, the advantage is that there is no delay in pulverizing the coal, it is possible to compensate for dead time and response delay, and it is possible to perform good fuel supply control.

Another embodiment of the invention is shown in FIG. In this embodiment, a blow-up means (air blow-off port) 15 is provided at the bottom of the classifier 6. This blow-up means (air outlet) 15 has an air pipe 63 that passes through the casing 62 of the vertical mill 2, and a nokuru 64 is added to the air pipe 63, and this pulp 64 is It is configured to be able to perform ON-OFF control.

During normal operation, the pulp 64 is kept in an OFF state, and during a load change, it is previously set in an ON state for a certain period of time to introduce air into the classifier 6. This amount of air is
It can be easily understood from FIG. 4 that the separation performance of the classifier 6 is extremely reduced when the amount of air supplied into the vertical mill 2 through the throat 11 shown in FIG. 3 is about 3 inches. There will be. In this way, as in the embodiment shown in FIG. 1, by drawing out the coal held in the vertical mill 2, it is possible to eliminate the pulverization delay when the load changes and compensate for dead time and response delay.

〔Effect of the invention〕

According to the present invention, a blow-up means is provided in the casing of a classifier in a vertical mill, and by controlling this blow-up means in advance, the coal held in the mill can be carried out, so that delays in grinding in the mill can be prevented, and Response delays due to delays can be avoided.

[Brief explanation of the drawing]

Figures 1 and 2 are enlarged vertical cross-sectional views of the main parts according to the embodiment of the present invention, Figure 3 is a schematic system diagram of a vertical mill system of a coal-fired couplant, and Figure 4 is the classification efficiency of the classifier. A characteristic curve diagram of the entrainment ratio, FIG. 5 is a control system diagram of a vertical mill system, and FIG. 6 is a schematic configuration diagram of a conventional vertical mill. 4.5...Crushing section, 6...Classifier, 7
...Coal feed pipe, 15...Blowing means. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] The coal from the coal feeding pipe is supplied to the crushing section of the mill installed on the outer periphery, and the crushed coal is guided to a classifier that separates it into coarse powder coal and pulverized coal. 1. A vertical mill which performs classification to the upper part of a classifier, characterized in that said classifier is provided with blow-up means for blowing up coal held within the mill.