JPH1085624A - Controller for vertical mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a vertical mill by which fine particles of uniform quality are obtained irrespective of the properties of material to be pulverized and a change in them. SOLUTION: A vertical mill 4 is constituted of a pulverizing table 11 to which material to be pulverized is fed on the upper surface, a mill motor 23 for rotatively driving the pulverizing table 11, pulverizing elements 14 for pulverizing the material to be pulverized on the pulverizing table 11 while pressurized, a pressurizing means 18 for pressurizing the pulverizing elements 14 to the pulverizing table 11 side, and a classifier 20 for separating the pulverized material into coarse particles and fine partncles. In this case, a control means for changing at least one of the pressurizing force of the pressurizing means 18 and the revolution of the pulverizing table 11 according to the quantity and properties of the material to be pulverized is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device, and more particularly to a control device for a vertical mill suitable for pulverizing various kinds of coal having different properties with high efficiency.

[0002]

2. Description of the Related Art As a dry pulverizer for producing pulverized coal fuel for a coal-fired boiler or the like, a ball mill for rotating a cylindrical container filled with countless balls and pulverizing it and a plurality of balls or rollers on a rotary table are used. There is a vertical mill in which the powder is rotated while being pressed to pulverize it, but the latter is often used because the pulverizing power is about 1/2 to 2/3 of the former.

A vertical mill is generally called a ring roller mill, a ballless mill, a bowl mill, or the like, depending on the structure of a pulverizing unit, that is, the structure of a pulverizing medium which is rotated by being pressed on a rotary table. Are the same.

Conventionally, this type of mill has a cyclone type classifier installed therein, and classifies pulverized coal into coarse powder and fine powder to produce pulverized coal having about 70 to 80% passing through a 200 mesh.

[0005] However, most of the coal currently used in Japan is imported coal in terms of price, and the coal tends to increase further in the future. These overseas coals also vary widely in their properties, and recently have a fuel ratio (fixed carbon /
The use of coal with a volatile content of 2 or more and oil coke with little volatile content is also increasing. Since these fuels are harder to burn than domestic coal having a fuel ratio of about 1, it is required to pulverize more finely than before. For this reason, in recent vertical mills, a rotary classifier that can classify finer than a cyclone classifier has come to be used.

FIG. 16 is an apparatus system diagram of a conventional pulverized coal-fired boiler having a vertical mill. This device uses combustion air A
A forced draft fan 1 for supplying an air preheater 2 for preheating the air A, the forced draft fan 3 for primary air for delivering preheated primary air A ₁ pressurized, the vertical mill 4, the A bunker 5 and a coal feeder 6 for charging coal into a vertical mill,
A boiler 7 and a burner 7a provided in the boiler 7. Coal milled in vertical mill within 4 in such a configuration is supplied to the burner 7a with the primary air A _1, it is burned in the boiler 7 together with the secondary air A ₂ fed from the air preheater 2 You.

The vertical mill 4 includes a primary air inlet hole 9 provided in a lower portion of a housing 8, a coal feed pipe 10 connected to the above-described coal feeder 6, and a portion below an opening of the coal feed pipe 10. A crushing table 11, a crushing ring 13 fixed to the crushing table 11, a plurality of rollers 14 supported on the crushing ring 13, and a pressure frame 15 for applying a load to the rollers 14. A pressurizing cylinder 18 for adjusting the pressing force via a spring frame 17 and a spring 16, a throat ring 19 having a large number of air ejection holes, and a rotary classifier 20 for classifying pulverized coal by a rotary blade 21. And a classifier motor 22 for driving the rotary classifier 20, a gear box 12 provided with gears for rotating the crushing table 11, and a mill motor 23. That.

Reference numeral 24 denotes a coal feed pipe for supplying pulverized coal fine particles to the burner 7a, 25 denotes a primary air damper, 38 denotes a primary air flow controller, 26 denotes a hot air damper, and 39 denotes a hot air flow controller. , 27 is a cold air damper,
40 is a cool air flow controller, 28 is a classifier rotational speed detector, 29 is a classifier rotational speed controller, 30 is a coal feed flow detector, 37 is a coal feed regulator, and 31 is a mill outlet air temperature detector. , 32 is a mill differential pressure detector, 33 is a pressurized cylinder pressure detector, 34 is a mill power detector, 35 is a primary air differential pressure detector, 36 is a primary air temperature detector, and 100 is a mill control device. In such a vertical mill, the grinding table 11 rotates at 20 to 40 rpm in conjunction with the gear.
The roller 14 is fixed by a support shaft, and the crushing table 1
The roller 14 is in contact with the crushing ring 13 integrated with the crusher 1 and the crushing table 11 rotates.

The coal (particle size: about 5 to 20 mm) supplied from the coal feed pipe 10 to the pulverizing table 11 passes through a gap between the pulverizing ring 13 and a roller 14 pressurized at a constant pressure by centrifugal force. Crushed.

On the other hand, the primary air A ₁ heated to about 300 ° C. is introduced from the primary air inlet hole 9 at the bottom, is supplied to the upper throat 19 a through the throat ring 19 having a large number of air ejection holes, and is The pulverized coal particles are transported upward as shown by arrow E.

The coarse particles among the coal particles transported upward are separated from the airflow as shown by the arrow F with the decrease in the air flow rate, and returned to the pulverizing table 11 again. Particles having a smaller particle diameter than the coarse particles rise along the housing 8 together with the primary air (primary classification), and the centrifugal force acting on the particles due to the rotation of the rotating blades 21 of the classifier 20 and the drag in the centripetal direction of the particles. Classified into fine powder and fine powder by balance. That is, the fine powder having a large centrifugal force acting on the particles is blown off to the outside of the classifier by the centrifugal force, flows down along the housing 8 (arrow G), and joins with the coarse particles classified in the above-described primary classifier. It is returned to the crushing table 11 again. On the other hand, the fine powder subjected to only a small centrifugal force passes through the gap between the classification blades 21 together with the airflow (arrow H), and is transported from the coal feed pipe 24 to the burner 7a (secondary classification).

FIG. 17 shows an example of the partial classification efficiency of a rotary classifier, that is, an example of the proportion of particles collected on the coarse side for each particle size. The characteristic is that the classification characteristics can be varied by the rotation speed of the classifier. That is.

As described above, in a vertical mill, a mill for controlling a coal supply amount, a primary air flow rate, a mill outlet air temperature and a classifier rotation speed in accordance with a fuel amount request signal FD from a boiler master (not shown). A control device is provided. That is, the coal feeder 6 is provided with the coal flow detector 30 and the coal feed regulator 37, and controls the amount of coal supplied to the vertical mill based on the fuel amount request signal FD. Further, the supply amount of the primary air A ₁ supplied to the vertical mill 4 includes a primary differential air pressure detector 35, it is detected by the primary air temperature detector 36, based on the fuel amount request signal FD, primary air The opening of the damper 25 is controlled by the primary air flow controller 38.

On the other hand, the outlet air temperature of the mill is detected by the outlet air temperature detector 31 of the mill, and the flow rate of the hot air C is adjusted by the hot air flow controller 39 for adjusting the opening of the hot air damper 26; It is controlled by adjusting the flow rate of the cold air D by the cold air flow controller 40 that adjusts the opening degree of the cooling air D.

Further, the rotary classifier 20 is provided with a classifier rotation speed detector 28 for detecting the rotation speed and a classifier rotation speed adjuster 29, and the classifier rotation speed is controlled based on the fuel amount request signal FD. Is done. Further, as an operation monitoring device of the vertical mill 4, a mill differential pressure between a lower portion of the throat ring 19 and an inlet of the classifier 20 is detected in order to grasp the amount of coal between the throat ring 19 and the classifier 20. A mill differential pressure detector 32, a pressurized cylinder pressure detector 33 for monitoring the pressure applied to the grinding roller, and a mill grinding power detector 34 such as a mill motor current and a motor wattmeter for monitoring the grinding power of the mill are provided. Is provided.

FIG. 18 shows the relationship between the amount of pulverization and the amount of 200 mesh passing through the mill outlet when coal having different pulverizability (HGI) is pulverized in the mill having the configuration shown in FIG. Curve (a) shows the crushing characteristics of the HGI 50 coal as described above, curve (b) shows the crushing characteristics of the HGI 40 coal, and curve (c) shows the crushing characteristics of the HGI 60 coal. From this figure, it can be seen that the particle size at the mill outlet largely depends not only on the amount of pulverized coal but also on the pulverizability.

FIG. 19 shows the HG in the configuration of FIG.
I is the same (HGI50), but shows the result of pulverizing coal supplied to the mill with different particle sizes under the same conditions. As is clear from this figure, the mill outlet particle size greatly depends not only on the amount of raw coal supplied to the mill, but also on the raw coal particle size, even when the HGI is constant.

FIG. 20 shows the relationship between the amount of pulverization (coal feed) by the vertical mill equipped with the above-mentioned rotary classifier and the amount of 200 mesh passing through the mill outlet. In this figure, the curve (a) is the pulverization characteristics of coal having a hard glove pulverizability index (HGI) of 50, and the classifier decreases the rotation speed set at the pulverization amount of 100% with the reduction of the pulverization amount. Due to the operation, there is no excessive pulverization in a low load (low pulverization amount) region as in the pulverization characteristics [curve (a ')] when the operation is performed at a constant rotation speed, that is, the pulverization is efficient. . This is because at low load the pulverizing capacity has a margin so that the particle size of the coal that has passed through the pulverizing section is finer than at high load, but if the rotation speed of the classifier is constant, the classification characteristics are constant and it is somewhat fine. The resulting particles are also recirculated to the mill and over-milled, but by reducing the rotational speed of the classifier to make the classification point coarse (see FIG. 17), over-milling can be avoided. In connection with this type, there is an attempt to further improve the response characteristics of the mill when the load changes, by adjusting the number of revolutions of the classifier according to the changing speed of the coal supply amount.

An example of this is disclosed in Japanese Patent Application Laid-Open No. 60-241976.
FIG. 22 shows the configuration. FIG.
, The flow rate of coal supplied from the coal feeder is determined by
And a classifier rotation speed request signal 501S obtained as a function of the coal supply flow rate signal 30S as shown in the block 501 is calculated by the classifier rotation speed calculator 501. Further, the coal supply flow rate signal 30S is differentiated with respect to time by the finer 502 to obtain a coal supply flow rate change speed, and the signal 502S is input to the rotation speed increase / decrease calculator 503.

The arithmetic unit 503 sets the increase / decrease of the rotation speed to 0 when the absolute value of the coal feed flow rate change speed signal 502S is smaller than the set value, and sets the rotation speed when the signal 502S is larger than the upper limit of the set range. Negative signal 503 decreasing speed
S, and if the signal 502S is smaller than the lower limit of the set range, a positive signal 503S for increasing the rotation speed is output, and the adder 507 adds the signal to the rotation speed request signal 501S from the rotation speed calculator 501. It is output as a rotation speed request signal 507S.

The rotation speed request signal 5 from the adder 507
07S and the difference between the rotation speed signal 28S detected by the rotation speed detector 28 are obtained by a subtractor 508, and the rotation speed increase / decrease amount request signal 500S is output to the classifier rotation speed controller 29.
Drive.

In the conventional example shown in FIG. 22, when the coal supply flow rate sharply increases, the arithmetic unit 501 causes the rotation speed request signal 501S to be larger than before the coal supply flow rate changes.
Is output, but the arithmetic unit 503 outputs a negative signal, that is, a rotation speed reduction signal. For this reason, the rotation speed of the classifier is temporarily reduced, the classification point of the classifier is coarsened, and the circulating particles in the mill are discharged instantaneously, so that the responsiveness of the mill is increased.

On the other hand, when the flow rate of coal supply decreases rapidly, the rotation speed of the classifier is once increased, so that the classification point becomes finer, the amount of circulation in the mill increases, and the amount discharged from the mill decreases rapidly. This improves the ability of the mill to follow load changes.

On the other hand, in the vertical mill as shown in FIG. 16, the milling capacity Q (t / h) of the mill is such that the rotation speed of the milling table is ω, the pressing force M for pressing the milling roller to the upper surface of the milling table, If the effective diameter is D _R , it is proportional to the product of these (Powder Technology, 33, 127, 1).
982). That is, it represented by QαM · ωD _R. Also, the mill grinding power of M _P is the mill grinding table diameter D _R
Is determined, it depends on M _P ∝Mω (Powder Tech
nology, 29, 263, 1981).

On the other hand, in a pulverized coal-fired boiler,
Mills around the table are arranged, and the boiler load is 100
In percent, the load on each mill is designed to be about 80-100%. That is, the pressing force M at the design point and the rotation speed ω of the crushing table are determined. However, in a pulverized coal-fired boiler, the output of the boiler is not constant, but the load is adjusted, and the boiler is usually operated at a load of 40 to 100%. It is. During this time, the load on each mill typically varies from 50 to 100%. Therefore, in low-load operation below the design point of the mill, it is isolated from the optimum operation conditions of the mill and wasteful energy is consumed (that is, the product of the pressing force M applied to the grinding roller and the rotation speed ω of the grinding table is large). Pass).

Furthermore, unlike the oil-fired boiler, the coal-fired boiler has a specific problem that the response of the mill is delayed in response to a change in load of the boiler. In order to solve such a problem, recently, a method of varying the pressing force to the pulverizing roller according to the amount of coal supplied to the mill (Japanese Patent Application Laid-Open Nos. 57-87855 and 59-169543) has been proposed. A method of varying the pressing force according to the changing speed of the coal supply amount (Japanese Patent Application Laid-Open No. 59-1)
6953), a method of varying the rotation speed of the grinding table according to the amount of coal supplied (Japanese Patent Laid-Open No. 59-193154), and a method of increasing the front-rear pressing force or the rotation speed of the grinding table when the load demand changes. ing. According to such a method, it is possible to reduce the power unit (kwh / t) and improve the load responsiveness for a single coal type having stable properties.

In order to avoid the above-mentioned excessive pulverization at a low load, a method of reducing the pulverization force at a low load, that is, a pulverizing roller in accordance with the amount of coal supplied to the mill or the speed of change of the amount of supplied coal is used. To adjust the pressing force to the
7-87855, JP-A-59-169543) and a method of adjusting the rotation speed of a pulverizing table according to the amount of coal supplied (JP-A-59-193154). In order to improve the load responsiveness, a method of adjusting the pressing force to the pulverizing roller in accordance with the changing speed of the amount of coal supplied to the mill (Japanese Patent Laid-Open No. 59-169543), A method of increasing the pressing force on the crushing roller or the rotation speed of the crushing table (JP-A-58-88042) is exemplified.

[0028]

However, in the conventional method of controlling a vertical mill, no consideration is given to fluctuations in the properties of the raw coal or coping with multiple coal types.

That is, coal is a typical heterogeneous substance composed of maceral (coal content) and mineral matter, and its properties differ greatly even if it is mined from the same mine or the same coal seam. Furthermore, fluctuations in water content and unevenness in particle size in coal yards and storage devices are always accompanied. In such a case, it is not only impossible to uniformly produce pulverized coal continuously with the above-mentioned conventional technology, but also it is difficult to reduce the pulverizing power according to the load fluctuation. In recent years, in power plants, the use of 10 to 20 coal types of coal has been increasing, but it is difficult to reduce the crushing power unit, and there is a possibility that the product particle size may decrease. Further, there is a problem that every time the type of coal is changed, an enormous amount of labor by trial and error is required to set the optimal operation conditions.

In the conventional vertical mill, the rotation speed of the classifier is controlled only by the amount of coal and the rate of change of the amount of coal. The grinding amount is not always constant and constantly varies. Therefore, not only the response of the mill to a change in load cannot always be improved, but there is also a problem that trouble such as hunting of the main steam temperature of the boiler occurs because the mill is not smooth (the load change speed is not kept constant). Further, as described above, when 10 to 20 coal types of coal are used alone or mixed, there is a problem that the load response characteristics of the mill are different at the time of coal type switching or before and after the coal type switching.

An object of the present invention has been made in view of the above-mentioned circumstances of the prior art, and over-pulverizes fine powder of uniform quality irrespective of the properties and fluctuations of the material to be ground such as coal. It is an object of the present invention to provide a control device for a vertical mill which can be manufactured at low cost without causing the production.

Another object of the present invention is to provide a vertical mill control device capable of improving the response of a mill to a change in load regardless of the properties of the material to be milled, such as being supplied to the mill, and fluctuations thereof. Is to provide.

[0033]

In order to achieve the above-mentioned object, a control device for a vertical mill according to the present invention comprises a pressurizing means for pressing a pressurizing means in accordance with an amount (supply amount or required amount) and a property of a material to be ground. A control means capable of changing at least one of the pressure and the rotation speed of the crushing table is provided.

In order to improve the responsiveness of the mill to changes in load, control means for varying the number of revolutions of the classifier can be provided in addition to the above configuration.

Further, the control of the pressing force of the pressurizing means and the control of the rotation speed of the pulverizing table are performed by controlling the supply amount of the pulverized material to the mill,
It can be performed based on each of the mill differential pressure and the mill grinding power.

The rotation speed of the classifier can be controlled based on the supply amount of the material to be milled to the mill and the differential pressure of the mill, and can be performed in consideration of the milling power. Also,
The mill differential pressure can be controlled to match the mill differential pressure set value.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the pressing force of the pressing means or the rotation speed of the crushing table is varied in accordance with the amount and properties of the material to be crushed, and an appropriate mill differential pressure is obtained. Therefore, it is possible to prevent the particle size of the pulverized material at the pulverized material outlet from becoming coarse regardless of the properties of the pulverized material, and to prevent the amount of the pulverized material from increasing.

The pressing force of the pressurizing means and the rotation speed of the crushing table can be quickly and appropriately adjusted by using the mill differential pressure and the mill crushing power, which are significantly affected by the supply amount and properties of the crushed material, as calculation conditions. Is controlled to a high mill differential pressure. The same applies to the control of the number of revolutions of the classifier. The classification diameter is adjusted so as to make the mill differential pressure appropriate, and the optimum pulverizing conditions are obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a control system for realizing claim 1 of the control device according to the present invention, and FIG. 2 shows a schematic structure of a vertical mill to which the control system of FIG. 1 is applied and a system diagram for a boiler. FIG. 3 is a block diagram showing the configuration of the pressure control device.

In FIG. 2, the same reference numerals are used for those having the same or the same functions as those in FIG. 16, and duplicate description will be omitted below.

The configuration of FIG. 2 is different from the configuration of FIG. 16 in that a pressurizing cylinder pressure regulator 41 is added and a cylinder pressure signal from a pressurizing cylinder pressure detector 33 is taken into a mill control device 100. The above configuration, the configuration in which the mill power signal from the mill power detector 34 is taken into the mill control device 100, and the configuration in which the mill differential pressure signal from the mill differential pressure detector 32 is transmitted to the mill differential pressure control device 100 The point is to take in.

In FIG. 1, a mill control device 100 includes a coal supply amount control device 200, a primary air amount control device 300,
Mill outlet air temperature control device 400 and pressing force control device 5
00.

The coal feed control device 200 operates so that the fuel demand signal FD and the coal feed flow signal 30S from the coal feed detector 30 coincide with each other. 37 is driven.

The primary air flow control device 300 outputs the primary air differential pressure signal 35 detected by the primary air differential pressure detector 35.
S, a primary air flow signal (not shown) obtained from the primary air temperature signal 36S detected by the primary air temperature detector 36, and a primary air flow request signal (not shown) obtained as a function of the fuel amount request signal FD. (Not shown) so that the primary air damper 25 operates according to the primary air damper opening request signal 300S.
Is adjusted, and the primary air flow rate is controlled. The mill outlet air temperature control device 400 includes: a mill outlet air temperature signal 31S detected by the mill outlet air temperature detector 31;
The operation is performed so that the mill outlet air temperature signal set by the mill outlet air temperature setter (not shown) matches, and the hot air flow controller 39 and the cold air damper opening are transmitted by the hot air damper opening request signal 400S. The cold air flow controller 40 is driven by the request signal 401S.

The pressurizing control device 500 is a setting mill which is obtained as a function of a standard pressurizing signal from the pressurizing cylinder 18 according to the fuel amount request signal FD and a coal feed flow signal 30S detected by the coal feed flow detector 30. In accordance with the pressure increase / decrease amount signal based on the difference between the differential pressure signal and the mill differential pressure signal 32S detected by the mill differential pressure detector 32, and the change speed of the coal supply flow rate detected by the coal supply flow rate detector 30. A pressing force request signal obtained based on the pressing force increase / decrease amount signal is a cylinder pressure signal 3 detected by the pressing cylinder pressure detector 35.
The operation is performed so that the actual pressure applied to the grinding roller is a function of 3S and the mill power signal 34S detected by the mill power detector 34 falls within a set value range. The pressurizing cylinder pressure regulator 41 is driven by the request signal 500S.

FIG. 3 is a block diagram showing details of the configuration of the pressure control device 500. The pressing force control device 500 includes:
A standard pressure calculator 502 for calculating a standard pressure on the basis of the fuel amount request signal FD; and a coal feed for obtaining a rate of change of the coal flow based on the coal flow signal 30S detected by the coal flow detector 30. A flow rate change speed calculator 503, a pressurizing force increase / decrease amount calculator 504 for calculating a pressurizing force increase / decrease amount based on the coal supply flow rate change speed signal 503 </ b> S obtained by the coal feed flow rate change speed calculator 503, A pressing force maximum increase / decrease amount setting unit 505 for setting the maximum value of the increase / decrease amount, a setting mill differential pressure calculator 506 for calculating the set mill differential pressure based on the coal supply flow rate signal 30S from the coal supply flow rate detector 30, Set mill differential pressure request signal 506S from set mill differential pressure calculator 506
Subtractor 507 for calculating a deviation between the signal and the mill differential pressure signal 32S from the mill differential pressure detector 32, and a process for calculating the pressure increase or decrease based on the mill differential pressure increase or decrease request signal 507S obtained by the subtractor 507. A pressure increase / decrease amount calculator 508 and a pressure increase / decrease amount setting device 50 for setting the maximum value of the pressure increase / decrease amount
9 and when the absolute value of the coal feed flow rate change rate calculator 503S from the coal feed flow rate change rate calculator 503S is equal to or smaller than a preset value, the pressure from the pressing force maximum change amount setter 509 is set. The pressure increase / decrease amount request signal 509S is output as a pressure increase / decrease amount request signal 510S. When the absolute value of the coal feed flow rate change speed signal 503S is larger than the set value, the pressure increase / decrease from the pressure increase / decrease setter 509 is increased. Signal limiter 5 that outputs quantity request signal 509S as 0
10, a pressing force increase / decrease amount request signal 510S from the signal limiter 510, a pressing force increase / decrease amount request signal 505S from the pressing force maximum change amount setting unit 505, and a standard pressing force request from the standard pressing force calculator 502. An adder 511 for obtaining the sum of the signals 502S, and a maximum pressure controller 512 for setting the maximum value of the pressure request signal 511S from the adder 511.
A signal converter 514 for calculating an actual pressing force for pressing the pulverizing roller based on the pressure cylinder pressure signal 33S detected by the pressure cylinder pressure detector 33;
14 and the actual pressurizing controller 51
Subtractor 513 for obtaining a deviation from the pressurizing force request signal 512S from the second pressure sensor 2, and a pressurizing cylinder pressure increasing / decreasing amount calculation for calculating the pressurizing cylinder pressure increasing / decreasing amount based on the pressing force increasing / decreasing amount request signal 513S from the subtractor 513. 515 and the subtractor 51
A mill power change calculator 516 for calculating the mill power change based on the pressure increase / decrease request signal 513S from
The mill power change signal 516S from the mill power change calculator 516 and the mill power signal 3 from the mill power detector 34
4S, a mill power limiter 518 for setting the maximum and minimum values of the set mill power signal 517S from the adder 517, and the mill power limiter 51.
The subtractor 5 calculates the deviation between the mill power request signal 518S from the adder 8 and the set mill power signal 517S from the adder 517.
19 and the mill power deviation signal 519 from the subtractor 519.
The pressurized cylinder pressure increase / decrease amount calculator 520 that calculates the correction amount of the pressurized cylinder pressure change amount based on S, and the pressurized cylinder pressure change amount correction amount request signal 520S from the pressurized cylinder pressure change amount calculator 520 From the pressurized cylinder pressure increase / decrease amount calculator 515
And a subtracter 521 for subtracting from 15S. The pressure cylinder pressure regulator 41 is driven by the pressure cylinder pressure increase / decrease amount request signal 500S from the subtractor 521.

Next, the operation of the configuration shown in FIG. 3 will be described with reference to FIGS. First, the standard pressing force for pressing the crushing roller of the vertical mill is applied to the standard pressing force calculator 502 in accordance with the fuel amount request signal FD from the boiler master.
, And the standard pressure signal 502S is sent to the adder 511.

FIG. 4 shows an example of the functional relationship between the amount of coal supplied to the mill, that is, the amount of pulverization, based on the fuel amount request signal FD, and the standard pressing force. Here, the standard pressure may vary depending on conditions such as the size of the mill and the type of crushing material, in addition to the amount of pulverization. Further, the change rate of the coal supply flow rate is calculated by the coal supply flow rate change speed calculator 503 based on the coal supply flow rate signal 30S detected by the coal supply flow rate detector 30. The coal feed flow rate change speed signal 503S obtained by the coal feed flow rate change rate calculator 503 is sent to the pressure increase / decrease amount calculator 504, and the pressure increase / decrease amount is calculated.

FIG. 5 shows an example of the functional relationship between the rate of change in the flow rate of coal feed and the amount of increase or decrease in the pressing force. In this figure, when the coal feed flow rate change rate is 0, that is, when the coal feed flow rate is constant, the pressure increase / decrease amount is 0, and when the change rate is negative, the increase / decrease is proportional to the absolute value. The negative absolute value of the pressure increase / decrease amount (that is, the pressure reduction amount) is set to be large (solid line curve a). The absolute value of the pressing force increase / decrease amount signal 504S from the pressing force increase / decrease amount calculator 504 is limited by the pressing force maximum change amount setting unit 505 so as to be equal to or less than the set maximum value, and sent to the adder 511.

An example of the functional relationship between the change rate of the coal supply flow rate and the increase / decrease amount of the applied pressure after the restricting process by the applied pressure maximum increase / decrease setter 505 is shown by a broken line curve b in FIG. Further, the set mill differential pressure is set by the set mill differential pressure calculator 506 based on the coal feed flow signal 30S from the coal feed flow detector 30.

Generally, the mill differential pressure in a vertical mill is determined mainly as a function of the coal supply flow rate and the primary air flow rate. The relationship between the coal supply flow rate and the primary air flow rate is represented by the relationship shown in FIG. Therefore, when the coal supply flow rate is given, the mill differential pressure is given in a functional relationship as shown in FIG. 7A, and the set mill differential pressure calculator 506 calculates the set mill differential pressure. Set mill differential pressure request signal 5 from set mill differential pressure calculator 506
06 is applied to the subtractor 507, and the deviation from the mill differential pressure signal 32 S detected by the mill differential pressure detector 32 is
07. Based on the mill differential pressure increase / decrease request signal 507S output from the subtracter 507, the pressure increase / decrease amount is calculated by the pressure increase / decrease amount calculator 508.

A curve (a) indicated by a solid line in FIG. 8 shows an example of a functional relationship between the increase / decrease amount of the mill differential pressure and the increase / decrease amount of the pressurization force calculated by the pressurization increase / decrease amount calculator 508. Pressing force increase / decrease amount calculator 508
The pressurizing force increase / decrease amount request signal 508S is limited to a maximum value by a pressing force maximum change amount setting unit 509. An example of a relationship between the mill differential pressure increase / decrease amount and the pressurization increase / decrease amount after the arithmetic processing is performed on the maximum pressurization amount 509 is shown by a broken line curve (b) in FIG.

The pressure increase / decrease amount request signal 509S from the pressure increase / decrease amount calculator 509 is supplied to the coal supply flow rate change speed calculator 50.
When the absolute value of the coal feed flow rate change speed signal 503S from 3 is equal to or less than the set value, it is output as it is as the output signal of the signal limiter 510.
Are output from the signal limiter 510 as adders 511
Sent to

The pressure increasing / decreasing amount request signal 510S from the signal limiter 510 is composed of a standard pressure requesting signal 502S based on the fuel amount request signal FD, a pressing force increasing / decreasing amount request signal 505S based on the coal feed flow rate changing speed, and an adder. Added at 511,
The pressing force request signal 512S is output after being limited to be equal to or less than the maximum pressing force set by the maximum pressing force controller 512. A subtractor 513 calculates a deviation between the applied pressure request signal 512S and the actual applied pressure signal 514S obtained by the signal converter 514 from the cylinder pressure signal 33S detected by the pressurized cylinder pressure detector 33.

The pressure increasing / decreasing amount request signal 513S from the subtractor 513 is sent to the cylinder pressure increasing / decreasing amount calculator 515 to be operated, and the cylinder pressure increasing / decreasing amount request signal 515S is output and sent to the subtractor 521.

FIG. 9 shows an example of the relationship between the amount of increase and decrease in pressure and the amount of increase and decrease in cylinder pressure. The pressure increase / decrease amount request signal 513S from the subtractor 513 is sent to the mill power change amount calculator 516 simultaneously with the cylinder pressure increase / decrease amount calculator 515, and the mill power change amount based on the pressure increase / decrease amount is calculated.
It is output as a mill power change amount signal 516S and input to the adder 517 together with the mill power signal 34S detected by the mill power detector 34.

FIG. 10 shows the amount of change in the mill power with the increase or decrease in the pressing force. Set mill power signal 517 from adder 517
S is sent to mill power limiter 518, where the mill power is limited to a value within the range set by the maximum and minimum values, and output as mill power request signal 518S. The difference between the mill power request signal 518S and the set mill power signal 517S is calculated by the subtractor 519, and the output of the mill power deviation signal 519S is output to the cylinder pressure increase / decrease amount calculator 52.
Input to 0. Cylinder pressure signal increase / decrease calculator 520
In, the correction value of the pressurized cylinder pressure change amount is calculated based on the mill power deviation signal 519S, and the cylinder pressure change amount correction request signal 520S is input to the subtractor 521.

FIG. 11 shows the relationship between the mill power deviation value and the cylinder pressure increase / decrease correction amount. The mill power is predicted from the cylinder pressure increase calculated by the pressurized cylinder pressure increase / decrease calculator 515. If the mill power exceeds the maximum mill power, the increase in the cylinder pressure is reduced. Further, when the mill power predicted by the cylinder pressure reduction amount becomes equal to or less than the minimum mill power value, correction is made so that the cylinder pressure reduction amount becomes small.

The subtractor 521 subtracts the cylinder pressure increase / decrease amount correction amount request signal 520S from the cylinder pressure increase / decrease amount request signal 515S from the cylinder pressure increase / decrease amount calculator 515, and outputs the same as the pressure increase / decrease amount request signal 500S. The pressure cylinder pressure regulator 41 is driven.

In this embodiment, when the coal feed rate to the mill is constant or when the rate of change of the coal feed rate is small, the pressurizing force increase / decrease calculator 5 based on the rate of change of the coal feed rate.
03 is 0 or a small value, and the crushing roller pressing force is determined based on the standard pressing force determined mainly based on the fuel amount request signal FD, the set mill differential pressure determined from the coal supply flow rate, and the actually measured milling pressure. The pressure difference is determined from the pressure increase / decrease amount calculated so that the differential pressures match, that is, if the measured mill differential pressure is larger than the set mill differential pressure, the pressure is increased and the measured mill differential pressure is set. If it is smaller than the value, the pressure is reduced.

Therefore, even when the amount of coal supplied to the mill is constant, if the properties of the supplied coal such as pulverizability, particle size distribution, and moisture change, the mill differential pressure changes (for example, the HGI value increases). When the pulverizability improves, the mill differential pressure decreases as indicated by the broken curve (b) in Fig. 7. When the HGI value decreases and the pulverizability deteriorates, the mill differential pressure decreases as indicated by the broken curve (c) in Fig. 7. This is a point different from the conventional example in that the pressure of the crushing roller can be automatically adjusted to the optimum value as described above. In the conventional example,
Each time the coal type changes, the appropriate pressing force under standard grinding conditions must be set based on actual operating experience,
In this embodiment, the optimum pressing force is set automatically.

On the other hand, when the coal supply flow rate sharply increases due to the fuel amount request signal FD, the actually measured mill differential pressure is always smaller than the set value due to the delay of pulverization. Fig. 8 of decrease in pressure force in the opposite direction
Is output by the signal limiter 510. When the coal supply flow rate decreases rapidly, a signal for increasing the pressurizing force is output, and the output signal is set to 0 by the signal limiter 510.

That is, when the coal supply flow rate changes abruptly, the pulverizing roller is determined based on the standard pressure set based on the fuel amount request signal FD and the pressure increase / decrease amount corresponding to the change rate of the coal supply flow rate. The pressing force is set. In this case, when the coal supply increases, the pressing force is always set higher than in the steady state after the increase, and when the coal supply decreases, the pressure is set lower than in the steady state after the decrease. Responsiveness becomes faster and a steady state can be reached in a short time. As a result, the system can quickly respond to coal property fluctuations.

In the above embodiment, the mill differential pressure set within the set mill power range based on the fuel amount request signal, the coal feed signal and the mill differential pressure signal is set to match the actually measured mill differential pressure. The pressure of the crushing roller was controlled, but based on the fuel amount request signal, the coal supply signal, and the mill differential pressure signal,
By changing the rotation speed of the crushing table instead of the pressing force on the crushing roller so that the mill differential pressure set within the set mill operation power range matches the actually measured mill differential pressure (not shown), It is possible to obtain the same effect as the above embodiment.

Further, in the case where the properties of the coal to be pulverized vary widely depending on the type of coal, etc., the pressure applied to the pulverizing roller and the pressure of the pulverizing table are adjusted so that the set mill differential pressure and the actually measured mill differential pressure match. It is also possible to vary both of the rotation speeds.

Next, FIG. 12 is a block diagram of a control system for realizing the control method according to claims 2 and 4 of the present invention. In the present embodiment, the same reference numerals are used for members having the same or the same functions as those in FIG. 1, and therefore, duplicate description will be omitted below.

This embodiment is characterized in that a classifier rotation speed controller 600 is provided to control the classifier rotation speed controller 29 in the configuration of FIG. Further, each output of the mill differential pressure detector 32 and the mill power detector 34 is input to the classifier rotation speed control device 600 instead of the pressurization control device 500.

The pressurizing control device 500 outputs a fuel amount request signal F
The pressing cylinder pressure request signal 500S is operated such that the pressing force request signal to the grinding roller obtained as a function of D and the actual pressing force obtained as a function of the cylinder pressure detected by the pressing cylinder pressure detector 33 match. Drives the cylinder pressure regulator 41.

The classifier rotation speed controller 600 includes a classifier standard rotation speed request signal corresponding to the fuel amount request signal FD,
Coal supply flow signal 30 detected by coal supply flow detector 30
A signal requesting an increase or decrease of the classifier rotation speed based on the change speed of S, a mill differential pressure request signal obtained as a function of the coal feed flow detected by the coal feed flow detector 30, and a mill differential pressure detector 3
2 is operated so that the sum of the classifier rotation speed increase / decrease request signal based on the deviation from the mill differential pressure signal 32S detected by the step 2 and the rotation speed signal 28S from the classifier rotation speed detector 28 match. The classifier rotation speed controller 29 is driven by the classifier rotation speed controller 600S.

Further, in the classifier rotation speed control device, the mill power change amount given as a function of the increase / decrease amount request signal of the classifier rotation speed and the pressing force control device 500
Is calculated as a function of the cylinder pressure increase / decrease amount request signal 500S and the sum of the mill power signal detected by the mill power detector 34, and monitors whether or not this is within the set range of the mill power value. If it is out of the range, the classifier rotation speed increase / decrease amount is corrected and output as the classifier rotation speed increase / decrease amount request signal 600S.

FIG. 13 is a block diagram showing details of the pressure control device 500. The pressurizing force control device 500 includes a pressurizing force calculator 531 for calculating the pressurizing force on the crushing roller based on the fuel amount request signal FD, and a pressurizing cylinder pressure detector 33.
Pressure calculator 532 for converting the cylinder pressure signal 33S from the compressor into the actual pressure applied to the crushing roller;
From the pressure request signal 531S from the pressure calculation unit 53
Subtractor 533 for subtracting the pressure signal 532S from
And a pressure increasing / decreasing amount request signal 533 from the subtractor 533.
A pressurizing cylinder pressure increase / decrease amount calculator 534 for calculating the increase / decrease amount of the pressurizing cylinder pressure from S.

The pressure cylinder pressure regulator 41 is driven by the pressure cylinder pressure variation request signal 500S from the pressure cylinder pressure variation calculator 534. The pressure cylinder pressure increase / decrease amount request signal 500S is simultaneously input to the classifier rotation speed control device 600.

FIG. 14 shows a classifier rotation speed control device 600.
FIG. 4 is a block diagram showing the details of. In the figure, a classifier rotation speed control device 600 includes a classifier rotation speed calculator 601 for setting a standard rotation speed of the classifier based on a fuel amount request signal FD, and a coal supply flow rate from a coal supply flow rate detector 30. Pulverizer 602 for calculating the change rate of the coal feed flow rate based on signal 30S, and classifier rotation speed for calculating the increase or decrease of the rotation speed of the classifier based on the coal feed flow rate change signal 602S from the finer 602 Increase / decrease amount calculator 603, setting mill differential pressure calculator 604 for calculating a set mill differential pressure based on coal feed flow signal 30S from coal feed flow detector 30, and setting from set mill differential pressure calculator 604 Mill differential pressure request signal 604S
A subtractor 605 for subtracting the mill differential pressure signal 32S from the mill differential pressure detector 32, and a classifier rotation for calculating an increase or decrease of the classifier rotational speed based on the mill differential pressure deviation signal 605S from the subtractor 605. Speed increase / decrease amount calculator 606, classifier standard rotation speed request signal 601S from classifier standard rotation speed calculator 601 and classifier rotation speed increase / decrease amount calculator 60
3, an adder 607 for adding the classifier rotation speed increase / decrease amount request signal 603S from the classifier rotation speed increase / decrease amount calculator 606, and a classifier from the adder 607. A subtractor 608 for subtracting the classifier rotation speed signal 28S from the classifier rotation speed detector 28 from the rotation speed request signal 607S, and a change in mill power based on the classifier rotation speed increase / decrease request signal 608S from the subtractor 608. Mill power change amount detector 609 for calculating the amount
A mill power change calculator 611 for calculating a change in mill power based on a pressurizing cylinder pressure increase / decrease request signal 500S from the pressing force control device 500; and a mill power change calculator 611 from the mill power change calculator 611. The change amount signal 611S, the mill power change amount signal 609S from the mill power change amount calculator 609, and the mill power signal 34 from the mill power detector 34.
S, an adder 610, a mill power limiter 612 for limiting the predicted mill power signal 610S from the adder 610 to a maximum value or less and a minimum value or more, and a mill power prediction signal 610S from the adder 610. Mill power limiter 61
Subtractor 6 for subtracting the mill power request signal 612S from
13 and the mill power deviation signal 613 from the subtractor 613
A classifier rotation speed increase / decrease amount corrector 614 for calculating the correction amount of the classifier rotation speed increase / decrease amount based on S, and a classifier rotation speed increase / decrease amount corrector from the classifier rotation speed increase / decrease request signal 608S from the subtracter 608. And a subtracter 615 for subtracting the classifier rotation speed increase / decrease correction amount signal 614S from the classifier 614. The classifier rotation speed controller 29 is driven by the classifier rotation speed increase / decrease request signal 600S from the subtracter 615.

Next, the operation of the configuration shown in FIGS. 12 to 14 will be described. First, a given pressing force for pressing the crushing roller 14 of the vertical mill 4 is calculated by the pressing force calculator 501 in accordance with the fuel amount request signal FD from the boiler master, and the calculated set pressing force and the pressing cylinder are calculated. The pressing force increase / decrease amount request signal 500S drives the pressurizing cylinder pressure regulator 41 so that the actual pressing force calculated from the cylinder pressure value detected by the pressure detector 33 matches (FIG. 13).

The relationship between the pressing force applied to the crushing roller 14 and the amount of crushing is calculated by the pressing force calculator 531 in FIG. 13, and has a functional relationship in which the pressing force increases as the amount of crushing increases. The pressing force can vary depending on the type of the crushing amount in addition to the mill size and the crushing amount, and the functional relationship of the pressing force calculator 501 can be manually set arbitrarily. Also, a pressurizing cylinder pressure increase / decrease request signal 500
S is input to the classifier rotation speed control device 600, and the amount of change in mill power according to the increase or decrease in the pressing force is calculated.

Next, the standard rotation speed of the rotary classifier 20 is also calculated by the classifier standard rotation speed calculator 601 shown in FIG. 14 based on the fuel amount request signal FD from the boiler master. The classifier standard rotation speed calculator 601 uses a functional relationship such that the rotation speed is increased so that the classification point of the classifier becomes finer as the coal supply flow rate increases (see FIG. 17).

The change rate of the coal supply flow rate detected by the coal supply flow rate detector 30 is calculated by the coal supply flow rate change rate calculator 602, and the classifier rotation speed is increased or decreased based on the coal supply flow rate change rate signal 602S. A classifier rotation speed increase / decrease amount of the amount calculator 603 is calculated. That is, when the change rate of the coal supply flow rate is 0, that is, when the coal supply flow rate is constant, the increase / decrease of the classifier rotation speed is set to 0.

When the change speed is positive, that is, when the fuel amount request signal of the boiler increases, the increase / decrease of the classifier rotation speed is set to a negative value. In this case, since the rotation speed of the classifier temporarily decreases and the classification point becomes coarse (see FIG. 17), the coal held inside the mill is immediately discharged and the load response of the mill is shown in FIG. It is faster than the conventional example.

On the other hand, when the change speed of the coal feed flow rate is negative, that is, when the fuel amount request signal of the boiler decreases, the increase / decrease amount of the classifier rotation speed is set to a positive value. That is, since the rotation speed of the classifier temporarily increases and the classification point becomes fine, the amount of coal circulating in the mill increases, and the response of the mill is faster than that of the conventional example shown in FIG.

Further, based on the coal feed flow signal 30S from the coal feed flow detector 30, the set mill differential pressure is calculated from the functional relationship as shown in the characteristic diagram in the block of the set mill differential pressure calculator 604. . That is, the operation mill differential pressure is set to increase as the amount of pulverization increases. Mill differential pressure request signal 604S from the set mill differential pressure calculator 604
, The mill differential pressure signal 32S detected by the mill differential pressure detector 32 is subtracted by the subtractor 605.

Next, when the deviation is positive as shown in the characteristic diagram in the block of the classifier rotation speed increase / decrease calculator 606 based on the deviation, that is, when the set mill differential pressure is larger than the actually measured value, Outputs a signal for increasing the rotation speed of the classifier 20. In this case, since the classification point becomes finer by increasing the rotation speed of the classifier 20 (see FIG. 17), the amount of circulating coal particles in the mill increases, and the mill differential pressure increases.

Conversely, when the deviation is negative, that is, when the measured mill differential pressure is larger than the set value, a signal for decreasing the rotation speed of the classifier 20 is output. In this case, by reducing the rotation speed of the classifier 20, the classification point becomes coarse (see FIG. 17), so that the circulation amount of the coal particles in the mill is reduced and the mill differential pressure is reduced. A classifier standard rotation speed signal 601S based on the fuel amount request signal FD, a classifier rotation speed increase / decrease amount request signal 603S based on the coal feed flow rate change speed,
The classifier rotation speed increase / decrease amount request signal 606S based on the deviation between the set mill differential pressure based on the coal supply flow rate and the actually measured value is added to the adder 60.
7, the classifier rotation speed signal 28S detected by the classifier rotation speed detector 28 is subtracted from the classifier rotation speed request signal 607S from the adder 607, and the classifier rotation speed increase / decrease request to be adjusted is obtained. The signal 608S is output.

Next, the rotation speed increase / decrease amount request signal 608
Based on S, the change in the mill power is calculated as shown in the characteristic diagram in the block of the mill power change calculator 609.
In other words, when the classifier rotation speed increase / decrease amount is a positive value,
The classification point becomes finer (see FIG. 6), and the circulating amount of the particles in the mill increases, so that the mill power increases. If the increase or decrease is a negative value, the classification point becomes coarse and the circulation amount in the mill decreases. Therefore, the mill power is reduced.

On the other hand, the mill power also changes due to a change in the pressing force applied to the pulverizing roller by the pressing cylinder pressure increase / decrease amount request signal 500S from the pressing force control device 500. Then, the pressurized cylinder pressure increase / decrease amount request signal 500S is taken into the mill power change amount calculator 611 to calculate the change amount of the mill power.

That is, as shown in the characteristic diagram in the block of the mill power change amount calculator 611, when the pressurized cylinder pressure increase / decrease amount is positive, the pressing force to the crushing roller increases, so that the driving power of the mill increases. However, when the increase / decrease amount is negative, the driving force of the mill decreases because the pressing force decreases. A mill power change signal 611S based on the pressurizing force change amount and a mill power change signal 611 based on the classifier rotational speed change amount.
S and the mill power signal 34S from the mill power detector 34 are added by an adder 610, and a predicted mill power signal 610S is output and input to the mill power limiter 612. In the mill power limiter 612, a mill power prediction signal 610S
Is within the set motion power range of the mill.
That is, when the mill power prediction signal 610S is equal to or more than the maximum value of the mill driving power, the maximum value is set, and when the signal is equal to or less than the minimum value, the minimum value is set.

The mill power request signal 612 S from the mill power limiter 612 is used as the expected mill power signal 6 from the adder 610.
The subtractor 613 subtracts from 10S, and based on the deviation, the correction amount of the classifier rotation speed increase / decrease amount is calculated as shown in the characteristic diagram in the block of the classifier rotation speed increase / decrease amount corrector 614. That is, when the mill power prediction signal 610S is larger than the mill power request signal 612S (when the deviation is positive), a positive correction amount is output, and the subtractor 615 outputs the classifier rotation speed increase / decrease request signal from the adder 608. 6
08S, the corrected classifier rotation speed increase / decrease amount request signal 600S is input to the classifier rotation speed controller 29.

On the other hand, when the deviation is negative, that is, when the expected mill power signal 610S is smaller than the required mill power signal 612S, a negative correction amount is output, and the subtractor 615 increases or decreases the rotational speed of the classifier from the adder 608. Quantity request signal 6
08S, the corrected classifier rotation speed increase / decrease amount request signal is output from the subtractor 615, and the classifier rotation speed controller 29 is driven.

In this embodiment, when the flow rate of the coal feed to the mill is constant or when the rate of change of the flow rate of the coal feed is small, the increase / decrease calculator of the rotation speed of the classifier based on the rate of change of the flow rate of the coal feed. Classifier rotation speed increase / decrease signal 603 from 603
S is 0 or a small value, and the rotation speed of the classifier 20 is mainly the standard rotation speed determined based on the fuel amount request signal FD, the set mill differential pressure determined from the coal supply flow rate, and the actually measured mill differential pressure. It is determined from the classifier rotation speed increase / decrease amount calculated to match.

Therefore, even when the flow rate of coal supplied to the mill is constant, if the properties of the supplied coal such as crushability, particle size distribution, water content, and ash content change, the circulation amount of coal particles in the mill varies. However, according to the embodiment of the present invention, the classifier 2 is set so that the mill differential pressure becomes a set value.
The point that the rotation speed of 0 can be automatically adjusted is different from the conventional example. Further, in the prior art, each time the type of coal changes, an appropriate value of the amount of pulverization and the rotation speed of the classifier 20 must be set based on actual operating experience, which requires enormous labor. According to this, what can be achieved automatically is different from the conventional example.

On the other hand, when the coal supply flow rate sharply increases due to the fuel amount request signal FD, a rotation speed increase signal is output from the classifier rotation speed increase / decrease amount calculator 606 as the coal supply flow rate increases. Since the rate of increase in the coal supply flow rate is large, the classifier rotation speed increase / decrease amount calculator 603 outputs a rotation speed reduction signal. As a result, the rotation speed of the classifier 20 once decreases, the rotation speed of the classifier 20 once decreases, the classification point of the classifier 20 becomes coarse (see FIG. 6), and the circulating particles in the mill are discharged instantaneously. Mill response delay is reduced.

Conversely, when the fuel amount request signal FD decreases sharply, a rotation speed decrease signal is output from the classifier rotation speed increase / decrease calculator 606 as the coal feed flow rate decreases.
Since the reduction rate of the coal supply flow rate is large, a rotation speed increase signal is output from the classifier rotation speed increase / decrease amount calculator 603.
As a result, the rotation speed of the classifier is temporarily increased, and
Since the classification point of the coal is fine, the amount of coal particles circulated in the mill increases, the amount discharged from the mill decreases, and the time of the response delay of the mill decreases. As described above, in this embodiment, even when the mill load changes rapidly, the mill quickly reaches a steady state because the responsiveness of the mill is fast, so that the mill system can quickly respond to coal property fluctuations. Becomes

In the present embodiment, the mill power is constantly monitored, and if the mill power exceeds the set range, the increase / decrease of the classifier rotation speed is corrected so that the mill power value falls within the set range. . Therefore, when the mill differential pressure does not fall within the set range, the pressing force control device 50
Since the set value of the pressing force calculator 501 of 0, the set value of the classifier standard pressing force calculator 601, the set value of the set mill differential pressure calculator, the set value of the mill power limiter 612, and the like can be manually changed. Mill optimization can be achieved efficiently.

Next, FIG. 15 shows a block diagram of a control system for realizing the control method according to the second, fifth and sixth aspects of the present invention. In the present embodiment, the same reference numerals are used for the same components as those in FIG.

The present embodiment is different from the configuration of FIG. 14 in that the mill power variation calculator 611 is eliminated and the configuration of FIG.
The request signal 500S for increasing or decreasing the pressure of the pressurizing cylinder from the pressurizing force control device 500 in Step 2
(Pressurizing cylinder pressure is manually set).

Therefore, the mill power change signal 611S is not added to the mill power prediction signal 610S.

Mill power change signal 60 from arithmetic unit 609
9S is a mill power signal 34S from the mill power detector 34.
And an adder 610. The mill power prediction signal 610S from the adder 610 is input to the mill power limiter 612, and is limited so as to be within the set range of the mill power. That is, if the mill power prediction signal 610S is equal to or more than the set maximum value, the signal is limited to the maximum value, and if it is equal to or less than the set minimum value, the signal is limited to the minimum value.

However, in this embodiment, since the mill power change amount signal 611S is not added, the pressure of the milling roller of the mill is not adjusted, but even in this case, the mill differential pressure is adjusted to the set value. The rotation speed of the classifier can be automatically adjusted, that is, the circulation amount of the coal particles in the mill can be automatically controlled, and the response of the mill to a change in load can be improved.

In the above embodiment, the signal 30S from the coal feed flow detector 30 was used for calculating the set mill differential pressure. However, the same effect can be obtained by using the fuel amount request signal FD instead. There is. Further, in FIG.
The fuel amount request signal FD is used for the calculation of the classifier rotation speed in Step 1.
Was used, but the same effect can be obtained by using the signal 30S from the coal supply flow rate detector 30 instead.

Further, in the configuration of FIG. 15, a circuit for detecting the mill power and correcting the increase or decrease of the rotation speed so that the mill power falls within the set value by the increase or decrease of the classifier rotation speed is provided. , If there is room in the mill motor, if it is not necessary to make the pulverized coal particle size extremely fine, or if you do not handle extremely poorly crushable coal,
Arithmetic units 509, 510, 511, 512, 513, 51
4 may be omitted, and a signal from the arithmetic unit 508 may be directly input to the rotation speed controller 29.

In the embodiments shown in FIGS. 1, 3, 12 and 14, the set mill power is set within the set mill power range based on the fuel amount request signal, the coal supply signal and the mill differential pressure signal. The pressing force of the crushing roller was controlled so that the differential pressure and the actually measured mill differential pressure coincided with each other, but based on the fuel amount request signal, the coal supply signal, and the mill differential pressure signal, the mill operation power range was set. In place of the pressing force on the crushing roller, the crushing table 11 is used so that the mill differential pressure set in the above step is equal to the actually measured mill differential pressure.
By varying the rotation speed (not shown), the same effect as in the embodiment shown in FIGS. 1 and 3 can be obtained.

Further, in the case where the properties of the coal to be pulverized vary widely depending on the type of coal, etc., the pressure applied to the pulverizing roller 14 and the pulverization table are adjusted so that the set mill differential pressure and the actually measured mill differential pressure match. It is also possible to vary both of the eleven rotation speeds.

[0102]

According to the present invention, there is provided a control means for varying at least one of the pressing force of the pressurizing means and the rotation speed of the crushing table in accordance with the amount and properties of the material to be crushed. Is provided, the mill can be economically and automatically operated irrespective of fluctuations in the properties of the material to be ground supplied to the mill.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment according to the present invention.

FIG. 2 is a schematic configuration of a vertical mill to which the present invention is applied and a system diagram of a boiler.

FIG. 3 is a block diagram illustrating a configuration of a pressing force control device.

FIG. 4 is an explanatory diagram showing a relationship between a pulverization amount and a primary air flow rate.

FIG. 5 is an explanatory diagram showing a relationship between a coal supply flow rate and a pressure increase / decrease amount.

FIG. 6 is an explanatory diagram showing the relationship between the amount of pulverization and the amount of primary air.

FIG. 7 is an explanatory diagram showing a relationship between a grinding amount and a mill differential pressure.

FIG. 8 is an explanatory diagram showing a pressure increase / decrease amount necessary for increasing / decreasing a mill differential pressure.

FIG. 9 is an explanatory diagram showing a cylinder pressure increase / decrease amount for increasing / decreasing a pressing force.

FIG. 10 is an explanatory diagram showing a mill power change amount with respect to a pressure increase / decrease amount.

FIG. 11 is an explanatory diagram showing a correction amount of a cylinder pressure increase / decrease amount based on mill power.

FIG. 12 is a block diagram showing a second embodiment of the present invention.

FIG. 13 is a block diagram illustrating details of a pressing force control device 500 according to a second embodiment.

FIG. 14 is a block diagram illustrating details of a classifier rotation speed control device 600 according to a second embodiment.

FIG. 15 is a block diagram showing a third embodiment of the present invention.

FIG. 16 is a system diagram of a conventional pulverized coal-fired boiler having a vertical mill.

FIG. 17 is an explanatory diagram showing a relationship between a partial classification efficiency and a rotation speed of the rotary classifier.

FIG. 18 is an explanatory diagram showing the effect of the HGI of coal on the load characteristics and the mill differential pressure of a vertical mill having a conventional rotary classifier.

FIG. 19 is an explanatory diagram showing the effect of the raw coal particle size on the load characteristics and the differential pressure of a conventional vertical mill.

FIG. 20 is an explanatory diagram showing the influence of coal pulverizability on load characteristics of a conventional vertical mill having a rotary classifier.

FIG. 21 is an explanatory diagram showing the influence of the particle size of raw coal on load characteristics of a vertical mill having a conventional rotary classifier.

FIG. 22 is a block diagram showing a configuration of a conventional classifier rotation speed control device.

[Explanation of symbols]

 Reference Signs List 4 vertical mill 6 coal feeder 7 boiler 9 primary air inlet hole 11 crushing table 14 crushing roller 18 pressurizing cylinder 20 rotary classifier 21 rotating blades 22 classifier motor 23 mill motor 29 classifier rotation speed controller 30 coal feed flow Detector 32 Mill differential pressure detector 33 Pressurized cylinder pressure detector 34 Mill power detector 37 Coal supply amount controller 41 Pressurized cylinder pressure regulator 100 Mill control device 200 Coal supply amount control device 300 Primary air control device 500 Pressure controller 600 Classifier rotation speed controller FD Fuel amount request signal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taku Oshima 3-36 Takara-cho, Kure-shi, Hiroshima Pref. Inside the Kure Laboratory (72) Inventor Tadashi Hasegawa 6-9 Takara-cho, Kure-shi, Hiroshima Babkotsuk Hitachi, Ltd. Inside the Kure Plant (72) Inventor Yoshinori Taoka 6-9 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Plant, Babkotsuk Hitachi, Ltd. (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure City, Hiroshima Prefecture Inside the Bab Kotsk Hitachi Kure Plant, Ltd.

Claims (1)

[Claims] 1. A grinding table to which an object to be ground is supplied on a top surface, a mill motor for rotating the grinding table, a grinding element for grinding the object to be ground while pressing the object on the grinding table, In a vertical mill equipped with a pressurizing means for pressing to the crushing table side and a classifier for separating the crushed material into coarse powder and fine powder, the pressing force of the pressing means according to the amount and properties of the crushed material And a control means for changing at least one of a rotation speed of the pulverizing table and a control device of the vertical mill.