JP7789553B2 - Operation control system, power plant, operation control method, and operation control program - Google Patents

Description

This disclosure relates to an operation control system, a power plant, an operation control method, and an operation control program.

Conventionally, solid fuels such as biomass fuel and coal are pulverized into fine powder within a specified particle size range in a pulverizer (hereinafter referred to as a "mill") and then supplied to a combustion device. In the mill, solid fuel is fed onto a grinding table and crushed between the grinding table and grinding rollers. From the finely pulverized solid fuel, fine particles within a specified particle size range are selected using a classifier. The fine particles are then transported to a boiler by carrier gas (primary air) supplied from the periphery of the grinding table, where they are combusted in the combustion device. In thermal power plants, steam is generated by heat exchange with the combustion gas produced by burning the pulverized fuel in the boiler. This steam drives a steam turbine, which in turn drives a generator connected to the steam turbine, generating electricity.

The operation of the mill is controlled according to the type of fuel supplied. When the type of fuel supplied changes, the combustion state of the boiler also changes, and the operation of the boiler is controlled accordingly (see, for example, Patent Document 1). The mill is controlled, for example, by an operator of the power plant manually selecting from multiple mill control modes that are prepared in advance corresponding to the type of fuel. Similarly, the boiler is controlled, for example, by an operator of the power plant manually selecting from multiple boiler control modes that are prepared in advance corresponding to the type of fuel. The selection of the control mode for the mill and boiler is performed independently of each other.

Japanese Patent Application Laid-Open No. 2019-132528

When the boiler control mode is selected manually at the discretion of the operator, boiler control may depend on the operator's experience. For example, depending on the operator's level of proficiency, the timing of changing the boiler control mode may differ significantly from the timing of changes in the boiler's actual combustion state. In the first place, it is difficult to determine the timing of changes in the boiler's combustion state using human judgment. In such cases, optimal control cannot be performed in accordance with the boiler's combustion state.

This disclosure was made in light of these circumstances, and aims to provide an operation control system and power plant, as well as an operation control method and operation control program, that can operate a boiler appropriately according to the characteristics of the fuel used.

A first aspect of the present disclosure is an operation control system for a power plant equipped with a boiler and multiple pulverizers, the operation control system including: a pulverizer control unit that controls the pulverizers based on a pulverizer control mode set for each pulverizer depending on the fuel supplied; a mode setting unit that sets a boiler control mode corresponding to a specified fuel when the number of pulverizers supplied with the specified fuel exceeds a threshold; and a boiler control unit that controls the boiler based on the boiler control mode.

A second aspect of the present disclosure is an operation control method for a power plant equipped with a boiler and multiple pulverizers, the operation control method including: a pulverizer control step for controlling the pulverizers based on a pulverizer control mode set for each pulverizer depending on the fuel supplied; a mode setting step for setting a boiler control mode corresponding to a specified fuel when the number of pulverizers supplied with the specified fuel exceeds a threshold; and a boiler control step for controlling the boiler based on the boiler control mode.

A third aspect of the present disclosure is an operation control program for a power plant equipped with a boiler and multiple pulverizers, the operation control program causing a computer to execute a pulverizer control process that controls the pulverizers based on a pulverizer control mode set for each pulverizer according to the fuel supplied; a mode setting process that sets a boiler control mode corresponding to a specified fuel when the number of pulverizers supplied with the specified fuel exceeds a threshold; and a boiler control process that controls the boiler based on the boiler control mode.

This disclosure has the effect of enabling the boiler to be operated appropriately according to the characteristics of the fuel used.

1 is a configuration diagram showing a solid fuel pulverizer and a boiler according to an embodiment of the present disclosure. FIG. 1 is a schematic configuration diagram illustrating an example of a hardware configuration of a driving control system according to an embodiment of the present disclosure. 1 is a functional block diagram illustrating functions of a driving control system according to an embodiment of the present disclosure. 10 is a flowchart illustrating an example of a procedure of a control process according to an embodiment of the present disclosure.

Below, one embodiment of an operation control system, power plant, operation control method, and operation control program according to the present disclosure will be described with reference to the drawings.

The power plant 1 according to this embodiment includes a solid fuel pulverizer 100 and a boiler 200 .
In the following explanation, "upper" refers to the vertically upward direction, and "upper" in terms such as upper part and upper surface refers to the vertically upward part. Similarly, "lower" refers to the vertically downward part, and the vertical direction is not precise and may include errors.

The solid fuel pulverizer 100 of this embodiment is an apparatus that pulverizes solid fuel (fuel) such as biomass fuel or coal, generates pulverized fuel, and supplies it to a burner (combustion device) 220 of a boiler 200, for example.
1 shows a single solid fuel pulverizer 100, but the power plant 1 including the boiler 200 is provided with a plurality of solid fuel pulverizers 100 corresponding to the plurality of burners 220 of the single boiler 200. For example, there are six stages of burners 220, and six solid fuel pulverizers 100 (i.e., mills 10) are provided corresponding to the burners of each stage (one of which is a spare, meaning that the total number of mills 10 in operation is five).

The solid fuel pulverizer 100 of this embodiment includes a mill (pulverizer) 10, a bunker (storage unit) 21, a coal feeder (fuel supplier) 25, a blower (carrier gas supplier) 30, and a status detector 40.

The mill 10, which pulverizes solid fuel such as coal or biomass fuel to be supplied to the boiler 200 into finely divided solid fuel, may be a type that pulverizes only coal, a type that pulverizes only biomass fuel, or a type that pulverizes both coal and biomass fuel.

Here, biomass fuel refers to renewable organic resources derived from living organisms, such as thinned wood, waste wood, driftwood, grasses, waste materials, sludge, tires, and recycled fuels (pellets and chips) made from these materials, but is not limited to the examples presented here. Biomass fuels are carbon-neutral, absorbing carbon dioxide during the biomass growth process and not emitting carbon dioxide, a greenhouse gas, and various uses are being considered. Among solid fuels, some biomass fuels, such as wood chips, are difficult to pulverize, while others have high combustibility and can be burned effectively even with relatively large particle sizes. When such biomass fuels are used as solid fuel in boiler 200, they are pulverized in mill 10 to a particle size approximately 5 to 10 times larger than that of coal and then supplied to burner 220 installed in boiler 200. As such, because the particle sizes of coal and biomass fuel supplied to the burner 220 are different, it is preferable that the mill 10 that pulverizes and classifies the solid fuel be controlled differently for biomass fuel pulverization and coal pulverization.

The mill 10 includes a housing 11, a grinding table 12, grinding rollers 13, a reducer (drive transmission unit) 14, a mill motor (drive unit) 15 connected to the reducer 14 and driving the grinding table 12 to rotate, a rotary classifier (classification unit) 16, a coal supply pipe (fuel supply unit) 17, and a classifier motor 18 that drives the rotary classifier 16 to rotate.
The housing 11 is formed in a cylindrical shape extending in the vertical direction, and is a case that accommodates the crushing table 12, the crushing rollers 13, the rotary classifier 16, and the coal supply pipe 17.
A coal feed pipe 17 is attached to the center of the ceiling portion 42 of the housing 11. This coal feed pipe 17 supplies solid fuel guided from the bunker 21 via the coal feeder 25 into the housing 11, and is arranged in the vertical direction at the center of the housing 11, with its lower end extending into the interior of the housing 11.

A reducer 14 is installed near the bottom surface 41 of the housing 11, and a mill motor 15 connected to the reducer 14 transmits a driving force to rotate the grinding table 12, which is rotatably disposed.
The grinding table 12 is a circular member in a plan view, and is disposed so as to face the lower end of the coal feed pipe 17. The upper surface of the grinding table 12 may, for example, have an inclined shape that is low in the center and rises toward the outside, with the outer periphery curved upward. The coal feed pipe 17 supplies solid fuel (for example, coal or biomass fuel in this embodiment) from above toward the grinding table 12 below, and the grinding table 12 pinches the supplied solid fuel between itself and the grinding rollers 13 to grind it.

When solid fuel is fed from the coal feed pipe 17 toward the center of the grinding table 12, the centrifugal force generated by the rotation of the grinding table 12 guides the solid fuel toward the outer periphery of the grinding table 12, where it is pinched and ground between the grinding table 12 and the grinding rollers 13. The ground solid fuel is blown upward by the carrier gas (hereinafter referred to as primary air) guided from the carrier gas flow path (hereinafter referred to as primary air flow path) 110, and is guided to the rotary classifier 16.
An outlet (not shown) is provided on the outer periphery of the grinding table 12, through which primary air flowing in from the primary air flow path 110 flows out into the space above the grinding table 12 within the housing 11. A swirl blade (not shown) is provided at the outlet, which imparts a swirling force to the primary air blown out from the outlet. The primary air imparted with the swirling force by the swirl blade becomes an airflow having a swirling velocity component, and transports the solid fuel pulverized on the grinding table 12 to the rotary classifier 16 located above in the housing 11. Note that, of the pulverized solid fuel, particles larger than a predetermined particle size are classified by the rotary classifier 16, or fall without reaching the rotary classifier 16 and are returned to the grinding table 12, where they are pulverized again between the grinding table 12 and the grinding rollers 13.

The crushing roller 13 is a rotating body that crushes the solid fuel supplied onto the crushing table 12 from the coal supply pipe 17. The crushing roller 13 is pressed against the upper surface of the crushing table 12 and cooperates with the crushing table 12 to crush the solid fuel.
1 shows only one representative crushing roller 13, but a plurality of crushing rollers 13 are arranged at regular intervals in the circumferential direction so as to press against the upper surface of the crushing table 12. For example, three crushing rollers 13 are arranged at equal intervals in the circumferential direction on the outer periphery at angular intervals of 120°. In this case, the portions of the three crushing rollers 13 that come into contact with the upper surface of the crushing table 12 (pressing portions) are equidistant from the central axis of rotation of the crushing table 12.

The crushing roller 13 can be swung and displaced up and down by the journal head 45, and is supported so that it can move toward and away from the upper surface of the crushing table 12. When the crushing table 12 rotates, the crushing roller 13 receives a rotational force from the crushing table 12 and rotates with it, with its outer peripheral surface in contact with the solid fuel on the upper surface of the crushing table 12. When solid fuel is supplied from the coal supply pipe 17, the solid fuel is pressed between the crushing roller 13 and the crushing table 12 and crushed. This pressing force is called the crushing load.

The support arm 47 of the journal head 45 is supported on the side of the housing 11 by a support shaft 48 whose middle section is horizontally aligned, allowing the crushing roller 13 to swing and move up and down around the support shaft 48. A pressing device (crushing load applying unit) 46 is provided at the upper end, vertically above the support arm 47. The pressing device 46 is fixed to the housing 11 and applies a crushing load to the crushing roller 13 via the support arm 47, etc., so as to press the crushing roller 13 against the crushing table 12. The crushing load is applied, for example, by a hydraulic cylinder (not shown) operated by the pressure of hydraulic oil supplied from a hydraulic device (not shown) installed outside the mill 10. The crushing load may also be applied by the repulsive force of a spring (not shown).

The reducer 14 is connected to the mill motor 15 and transmits the driving force of the mill motor 15 to the grinding table 12, causing the grinding table 12 to rotate around its central axis.

The rotary classifier (classification unit) 16 is provided at the top of the housing 11 and has a hollow, inverted cone-like outer shape. The rotary classifier 16 is provided with a plurality of blades 16a extending in the vertical direction around its outer periphery. The blades 16a are provided at predetermined intervals (equally spaced) around the central axis of the rotary classifier 16.
The rotary classifier 16 is a device that classifies the solid fuel pulverized by the pulverizing table 12 and the pulverizing rollers 13 (hereinafter, the pulverized solid fuel will be referred to as "pulverized fuel") into particles larger than a predetermined particle size (for example, 70 to 100 μm for coal) (hereinafter, pulverized fuel exceeding the predetermined particle size will be referred to as "coarse pulverized fuel") and particles smaller than the predetermined particle size (hereinafter, pulverized fuel smaller than the predetermined particle size will be referred to as "fine pulverized fuel"). The rotary classifier 16 is given a rotational driving force by a classifier motor 18 and rotates around a coal feed pipe 17, centered on a cylindrical axis (not shown) that extends in the vertical direction of the housing 11.
The classifying section may be a fixed classifier having a fixed hollow inverted cone-shaped casing and a plurality of fixed swirl vanes on the outer periphery of the casing instead of the blades 16a.

When the pulverized fuel reaches the rotary classifier 16, due to the relative balance between the centrifugal force generated by the rotation of the blades 16a and the centripetal force of the primary air flow, large diameter coarse pulverized fuel particles are knocked down by the blades 16a and returned to the grinding table 12 for re-pulverization, while the fine pulverized fuel is directed to the outlet port 19 in the ceiling 42 of the housing 11. The fine pulverized fuel classified by the rotary classifier 16 is discharged from the outlet port 19 along with the primary air into the fine pulverized fuel supply flow path (fine pulverized fuel supply pipe) 120 and supplied to the burner 220 of the boiler 200.

The coal feed pipe (fuel supply unit) 17 is attached so that its lower end extends vertically into the interior of the housing 11, penetrating the ceiling 42 of the housing 11. Solid fuel is fed from the top of the coal feed pipe 17 and supplied to the center of the grinding table 12. A coal feeder 25 is connected to the upper end of the coal feed pipe 17, and solid fuel is supplied.

The coal feeder 25 is connected to the bunker 21 by a downspout 22, which is a pipe extending vertically from the lower end of the bunker 21. A valve (coal gate, not shown) for switching the discharge state of solid fuel from the bunker 21 may be provided midway through the downspout 22. The coal feeder 25 includes a conveying unit 26 and a coal feeder motor 27. The conveying unit 26 is, for example, a belt conveyor, and uses the driving force of the coal feeder motor 27 to convey solid fuel discharged from the lower end of the downspout 22 to the top of the coal feed pipe 17 and deposit it inside. The amount of solid fuel supplied to the mill 10 is controlled, for example, by adjusting the movement speed of the belt conveyor of the conveying unit 26.

Normally, primary air is supplied to the inside of the mill 10 to transport pulverized fuel to the burner 220, and the pressure is higher than that of the coal feeder 25 and bunker 21. Inside the downspout section 22, which connects the bunker 21 and coal feeder 25, fuel is layered. This solid fuel layer ensures a seal (material seal) that prevents the primary air and pulverized fuel from flowing back from the mill 10 toward the bunker 21.

Biomass fuels, such as wood chips and wood pellets, have a uniform size before pulverization compared to coal. For example, coal before pulverization is in the form of chunks measuring 2 to 50 mm, while wood pellets are cylindrical and homogeneous, measuring 6 to 8 mm in diameter and 40 mm or less in length. When coal is stacked in the downspout 22, smaller coal particles fill the gaps between larger coal particles, resulting in a densely stacked state. On the other hand, when biomass fuel is stacked in the downspout 22, its size is uniform compared to coal, preventing the gap-filling effect of particles of different sizes, and resulting in larger gaps between the biomass fuel particles. Therefore, the primary air and pulverized fuel inside the mill 10 pass through the gaps formed in the solid fuel layer in the downspout 22, causing a backflow from inside the mill 10 through the coal feeder 25 and the downspout 22 to the bunker 21, resulting in a decrease in pressure inside the mill 10. This is more likely when using biomass fuel than when using coal fuel.
Furthermore, if the primary air and pulverized fuel flow back toward the bunker 21 and the pressure inside the mill 10 drops, various problems may arise in the stable operation of the solid fuel pulverizing device 100 and the boiler 200, such as a deterioration in the transportability of the pulverized fuel inside the mill 10, the generation of dust inside the coal feeder 25 and at the top of the bunker 21, ignition of solid fuel inside the coal feeder 25, bunker 21, or downspout section 22, and a decrease in the amount of pulverized fuel transported to the burner 220.
For this reason, a rotary valve (not shown) may be provided in the middle of the coal supply pipe 17 connecting the coal supply machine 25 to the inside of the mill 10 to suppress the occurrence of backflow of primary air and pulverized fuel from the inside of the mill 10 through the coal supply machine 25 and downspout section 22 to the bunker 21.

The blower 30 is a device that blows primary air into the housing 11 to dry the pulverized fuel and transport it to the rotary classifier 16 .
In order to appropriately adjust the flow rate and temperature of the primary air blown into the housing 11, in this embodiment, the blower 30 includes a primary air fan (PAF) 31, a hot gas flow path 30a, a cold gas flow path 30b, a hot gas damper 30c, and a cold gas damper 30d.

In this embodiment, the hot gas flow path 30a supplies a portion of the air sent out from the primary air ventilator 31 as hot gas that has been heated by passing through an air preheater (heat exchanger) 34. A hot gas damper 30c is provided in the hot gas flow path 30a. The opening degree of the hot gas damper 30c is controlled. The flow rate of the hot gas supplied from the hot gas flow path 30a is determined by the opening degree of the hot gas damper 30c.

The cold gas flow path 30b supplies a portion of the air sent out from the primary air ventilator 31 as cold gas at room temperature. A cold gas damper 30d is provided in the cold gas flow path 30b. The opening degree of the cold gas damper 30d is controlled. The flow rate of the cold gas supplied from the cold gas flow path 30b is determined by the opening degree of the cold gas damper 30d.

In this embodiment, the flow rate of the primary air is the sum of the flow rate of the hot gas supplied from the hot gas flow path 30a and the flow rate of the cold gas supplied from the cold gas flow path 30b, and the temperature of the primary air is determined and controlled by the mixing ratio of the hot gas supplied from the hot gas flow path 30a and the cold gas supplied from the cold gas flow path 30b.
Furthermore, the oxygen concentration in the primary air blown from the primary air flow path 110 into the housing 11 may be adjusted by, for example, introducing a portion of the combustion gas discharged from the boiler 200 by a gas recirculation fan (not shown) into the hot gas supplied from the hot gas flow path 30a and mixing it. By adjusting the oxygen concentration in the primary air, for example, when a highly ignitable (easily ignited) solid fuel is used, it is possible to prevent the solid fuel from igniting on the path from the mill 10 to the burner 220.

The state detection unit 40 of this embodiment is, for example, a differential pressure measuring means, which measures the differential pressure of the mill 10 as the pressure difference between the pressure at the portion where primary air flows into the housing 11 from the primary air flow path 110 and the pressure at the outlet port 19 where the primary air and pulverized fuel are discharged from the housing 11 to the pulverized fuel supply pipe 120. An increase or decrease in this differential pressure of the mill 10 corresponds to an increase or decrease in the amount of pulverized fuel circulating between the vicinity of the rotary classifier 16 inside the housing 11 and the vicinity of the grinding table 12 due to the classification effect of the rotary classifier 16. That is, by adjusting the rotation speed of the rotary classifier 16 in accordance with the differential pressure of the mill 10, the amount and particle size range of the pulverized fuel discharged from the outlet port 19 can be adjusted. Therefore, the particle size of the pulverized fuel can be maintained within a range that does not affect the combustibility of the solid fuel in the burner 220, and an amount of pulverized fuel corresponding to the amount of solid fuel supplied to the mill 10 can be stably supplied to the burner 220 provided in the boiler 200.
The state detection unit 40 of this embodiment is, for example, a temperature measurement means that detects the temperature of the primary air supplied to the inside of the housing 11 (mill inlet primary air temperature) and the temperature of the mixed gas of primary air and pulverized fuel at the outlet port 19 (mill outlet primary air temperature), and controls the blower unit 30 so that the respective upper limit temperatures do not exceed them. Each upper limit temperature is determined taking into consideration the possibility of ignition depending on the properties of the solid fuel. Note that, because the primary air is cooled inside the housing 11 by drying the pulverized fuel while transporting it, the primary air temperature at the mill inlet is, for example, from room temperature to approximately 300°C, and the primary air temperature at the mill outlet is, for example, from room temperature to approximately 90°C.

Next, we will explain the boiler 200, which generates steam by burning pulverized fuel supplied from the solid fuel pulverizer 100. The boiler 200 is equipped with a furnace 210 and a burner 220.

The burner 220 is a device that burns pulverized fuel to form a flame using a mixture of pulverized fuel and primary air supplied from the pulverized fuel supply pipe 120 and secondary air supplied by heating air (outside air) delivered from the forced draft fan (FDF) 32 in an air preheater 34. The pulverized fuel is burned in the furnace 210, and the high-temperature combustion gas passes through heat exchangers (not shown), such as an evaporator, superheater, and economizer, before being discharged outside the boiler 200.

The combustion gas discharged from the boiler 200 undergoes predetermined treatment in environmental equipment (such as a denitration device, dust collector, and desulfurization device, not shown), and then undergoes heat exchange with primary air and secondary air in an air preheater 34. The gas is then guided to a chimney (not shown) via an induced draft fan (IDF) 33 and released into the outside air. The air heated by the combustion gas in the air preheater 34 and delivered from the primary air fan 31 is supplied to the above-mentioned hot gas flow path 30a.
The water supplied to each heat exchanger of the boiler 200 is heated in a coal economizer (not shown), and then further heated in an evaporator (not shown) and a superheater (not shown) to generate high-temperature, high-pressure superheated steam, which is sent to the steam turbine (not shown), which is the power generation section, to rotate and drive the steam turbine, which then rotates and drives a generator (not shown) connected to the steam turbine, thereby generating electricity, thereby constituting the power generation plant 1.

The solid fuel used is not limited to that disclosed herein, and coal, biomass fuel, petroleum coke (PC), etc. can also be used. Furthermore, a combination of these solid fuels may also be used.

Next, the operation control system 80 will be described.
The operation control system 80 controls the operation of the boiler 200 and each mill 10 .

Figure 2 is a schematic diagram showing an example of the hardware configuration of an operation control system 80 according to one embodiment of the present invention. As shown in Figure 1, the operation control system 80 is a so-called computer, and includes, for example, a CPU (Central Processing Unit) 1100, main memory 1200, a storage unit 1300, an external interface 1400, a communication interface 1500, an input unit 1600, and a display unit 1700. These units are interconnected directly or indirectly via a bus, and work together to execute various processes.

The CPU 1100 controls the entire operation control system 80 using, for example, an OS (Operating System) stored in the memory unit 1300 connected via a bus, and performs various processes by executing various programs stored in the memory unit 1300.

Main memory 1200 is composed of writable memory such as cache memory or RAM (Random Access Memory), and is used as a working area for reading programs executed by CPU 1100 and writing data processed by the programs.

Memory unit 1300 is a non-transitory computer-readable storage medium, such as a ROM (Read Only Memory), HDD (Hard Disk Drive), or flash memory. Memory unit 1300 stores, for example, an operating system (OS) for controlling the entire device, such as Windows (registered trademark), iOS (registered trademark), or Android (registered trademark), a BIOS (Basic Input/Output System), various device drivers for operating peripheral hardware, various application software, and various data and files. Memory unit 1300 also stores programs for implementing various processes and various data required for implementing various processes.

The external interface 1400 is an interface for connecting to an external device. Examples of external devices include an external monitor, USB memory, and an external HDD. Note that although only one external interface is shown in the example shown in Figure 2, multiple external interfaces may be provided.

The communication interface 1500 functions as an interface for connecting to a network to communicate with other devices and sending and receiving information.
For example, the communication interface 1500 communicates with other devices via wired or wireless communication. Examples of wireless communication include Bluetooth (registered trademark), Wi-Fi, and communication using a dedicated communication protocol. An example of wired communication is a wired local area network (LAN).

The input unit 1600 is a user interface for giving instructions to, for example, a keyboard, mouse, touchpad, etc.

The display unit 1700 may be, for example, a liquid crystal display, an organic electroluminescence (EL) display, or the like. The display unit 1700 may also be a touch panel display with a touch panel superimposed thereon.

Figure 3 is a functional block diagram showing the functions of the operation control system 80. As shown in Figure 3, the operation control system 80 mainly comprises a mill control unit 81, a mode setting unit 82, and a boiler control unit 83.

The functions realized by each of these units are realized, for example, by processing circuitry. For example, the series of processes for realizing the functions shown below are stored in the storage unit 1300 in the form of a program, and the CPU 1100 reads this program into the main memory 1200 and executes information processing and arithmetic operations to realize the various functions.

The program may be pre-installed in the storage unit 1300, provided in a state stored on other computer-readable storage media, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

Each mill 10 is supplied with a specific type of solid fuel. In the transient state when switching from supplying one type of solid fuel to another type of solid fuel, the solid fuel discharged from the mill 10 to the boiler 200 is a mixture of two types of fuel. If a control mode corresponding to the mixed fuel is prepared in advance, the mixed fuel can be treated as a single type of fuel.

The mill control unit (grinding control unit) 81 controls the mill 10 based on the mill control mode. The mill control mode is set for each mill 10 depending on the type of solid fuel supplied to each mill 10.

Multiple mill control modes are prepared in advance and correspond to the type of solid fuel. To set the mill control mode, for example, an operator determines the supply status of the solid fuel and selects the mill control mode corresponding to the solid fuel. The mill control unit 81 then controls the mill 10 according to the selected mill control mode.

The mill control mode is a control mode set to optimize the operating state of the mill 10 according to the characteristics of the solid fuel being supplied. For this reason, the mill control mode is associated with control parameters of the mill 10. Control parameters are parameters used to control the mill 10, such as the primary air flow rate and classifier rotation speed. In the mill control mode, control values (set values) for each control parameter are set according to the characteristics of the solid fuel. As a result, the mill control unit 81 can optimize the operating state of the mill 10 according to the characteristics of the solid fuel by operating the mill 10 with reference to the control parameters of the set mill control mode. The values of each control parameter in the mill control mode are set for each type of solid fuel, for example, through a trial run.

For example, when coal (bituminous coal or sub-bituminous coal) and biomass fuel are used as solid fuels, a mill control mode corresponding to bituminous coal, a mill control mode corresponding to sub-bituminous coal, and a mill control mode corresponding to biomass fuel are prepared in advance.

In the above example, the mill control mode is selected at the discretion of the operator, but the mill control mode may also be set automatically depending on the type of solid fuel supplied to the mill 10. For example, when the type of solid fuel stored in the bunker 21 is switched, the bunker level corresponding to the switching point may be recorded, and the mill control mode may be automatically switched when solid fuel at that level reaches the coal feeder 25, or when a certain amount of time has passed since it reached the coal feeder 25 (taking into account the time it takes for the solid fuel to be supplied to the mill 10 after switching, crushed, and discharged from the mill 10).

The mode setting unit 82 sets the boiler control mode corresponding to the specified solid fuel when the number of mills 10 supplied with the specified solid fuel (specific solid fuel) exceeds a threshold value. In other words, the mode setting unit 82 automatically sets the boiler control mode based on the solid fuel supplied and the number of mills 10 (number of operating mills).

Specifically, the number of mills 10 to which a given solid fuel is supplied is determined using the number of mill control modes set for that given solid fuel. For example, if bituminous coal is supplied to three mills 10, a mill control mode corresponding to bituminous coal is set for each of these three mills 10. In other words, because three mill control modes corresponding to bituminous coal are set for multiple mills 10, the number of mills 10 to which bituminous coal is supplied (three) can be easily determined.

The threshold value is set according to the characteristics of a predetermined type of solid fuel (predetermined solid fuel). In other words, when multiple types of solid fuel are used, a threshold value is set corresponding to each of the multiple solid fuels. Then, when the number of mills 10 supplied with a predetermined solid fuel reaches or exceeds a threshold value (the threshold value corresponding to that predetermined solid fuel), a boiler control mode corresponding to that predetermined solid fuel is set. For example, the boiler control mode is set to a boiler control mode corresponding to bituminous coal, a boiler control mode corresponding to subbituminous coal, or a boiler control mode corresponding to biomass fuel.

Specifically, when the solid fuel is coal (bituminous coal or sub-bituminous coal), the threshold is set as the majority of the operating mills 10. Note that a majority is the integer that is greater than half the number of operating mills 10 and is closest to that half value. If the number of operating mills 10 fluctuates depending on the operating conditions, the threshold also fluctuates. Taking bituminous coal as an example, if there are five operating mills 10 and the number of mills 10 supplied with bituminous coal is three or more (the majority), the boiler control mode corresponding to bituminous coal is set.

For example, if the solid fuel is biomass fuel, the threshold is set to 1. In other words, when the number of mills 10 supplied with biomass fuel is 1 or more, the boiler control mode corresponding to biomass fuel is set.

The threshold value is preferably set according to the degree of influence on the operation of the boiler 200. The degree of influence refers to the degree of influence on the combustion state inside the furnace of the boiler 200, and the more easily the combustion state is changed, the higher the degree of influence. Solid fuels with a high degree of influence (e.g., biomass fuel) are more likely to change the combustion state of the boiler 200, so the higher the degree of influence of the solid fuel, the lower the threshold value is preferably set.

The boiler control mode is a control mode set so that the operating state of the boiler 200 is appropriate for the solid fuel being used. For this reason, control parameters of the boiler 200 are associated with the boiler control mode. Control parameters are parameters used to control the boiler 200. In other words, the boiler control mode has control values (set values) for each control parameter set according to the type of solid fuel being supplied. By operating the boiler 200 with the control parameters of the set boiler control mode, the operating state of the boiler 200 can be optimized according to the type of solid fuel. The values of each control parameter in the boiler control mode are set for each solid fuel, for example, through prior testing.

Control parameters in the boiler control mode are parameters used to control each piece of equipment that makes up the water/steam system, ventilation (air/exhaust gas) system, fuel/burner system, etc. in boiler 200, as well as various parameters used to change the operating state of boiler 200, such as advance control signals that are taken into account when the load changes. Specifically, the control parameters for each device include various settings such as steam superheat setting, steam separator inlet fluid temperature setting, boiler outlet oxygen concentration setting, soot blower operation setting, burner damper (secondary air damper, auxiliary air damper, additional air damper, wind box inlet damper, etc.) opening setting, burner nozzle angle setting, additional air nozzle setting, heater/reheater spray water control valve opening setting, superheater/reheater inlet/outlet steam temperature setting, exhaust gas distribution damper opening setting, boiler outlet exhaust gas damper opening setting and denitration ammonia injection control setting, and various settings for advance control during load changes such as feedwater flow rate BIR, fuel flow rate BIR, air flow rate BIR, various damper opening BIR, denitration ammonia injection BIR, steam temperature control BIR, pulverizer/classifier rotation speed BIR, primary air flow rate BIR, burner angle BIR, etc. Note that BIR stands for Boiler Input Ratio.

The boiler control unit 83 controls the boiler 200 based on the boiler control mode. Specifically, the boiler control unit 83 controls the boiler 200 based on the control parameters of the boiler 200 associated with the boiler control mode. This optimizes the operating state of the boiler 200 according to the characteristics of the solid fuel being used.

The boiler control unit 83 controls the boiler 200 based on the boiler control mode set by the mode setting unit 82, and may switch the boiler control mode. For example, this may involve switching from a boiler control mode suitable for bituminous coal to a boiler control mode suitable for sub-bituminous coal. When such a switch is made, the control values of the control parameters change, which in turn changes the combustion state within the furnace of the boiler 200.

However, if the combustion state inside the furnace changes suddenly, the operating state of the boiler 200 may become unstable. For this reason, when switching the boiler control mode, the boiler control unit 83 changes the control parameters of the boiler 200 over a predetermined period of time to change the operating state of the boiler 200. In other words, the control parameters are adjusted so that they do not change suddenly.

The operating state of the boiler 200 is changed over a predetermined time period (gradual change). For example, the change is made using a predetermined rate of change (speed of change). The speed of change is set in advance so that it can follow, for example, a change in mode (i.e., a change in the type of solid fuel) and ensures stability in the operation of the boiler 200 (no disturbance occurs). The speed of change may also be set for each control parameter depending on the boiler control mode switching pattern (such as a change from bituminous coal to sub-bituminous coal, or from bituminous coal to biomass fuel).

Next, a specific example of control by the operation control system 80 will be described.
For example, suppose that the solid fuel supplied to five mills 10 is switched from bituminous coal to subbituminous coal. In this case, bituminous coal is initially supplied to all five mills 10, and from this state, each mill 10 is switched in turn to supply subbituminous coal, until finally subbituminous coal is supplied to all five mills 10.

In this process, let's say there are three mills 10 that are supplied with bituminous coal and three mills 10 that are supplied with sub-bituminous coal. In this case, the mill control mode corresponding to bituminous coal is set for the two mills 10, and the mill control mode corresponding to sub-bituminous coal is set for the three mills 10.

When this happens, the number of mills 10 supplied with subbituminous coal will be more than half (three) (the number of mill control modes set for subbituminous coal will be more than half), so a boiler control mode for subbituminous coal will be automatically set, and the boiler 200 will be controlled based on this boiler control mode.

In the case of bituminous coal and sub-bituminous coal, the characteristics of the fuel that makes up the majority of the total coal become dominant in the combustion state inside the furnace of the boiler 200, so the above processing allows the boiler control mode to be switched appropriately.

Next, another specific example of control by the operation control system 80 will be described.
For example, suppose five mills 10 are being supplied with a certain solid fuel (not biomass fuel) and are switched to biomass fuel.

During this process, let's say that the number of mills 10 to which biomass fuel is supplied has decreased to one. In this case, a mill control mode corresponding to biomass fuel is set for that one mill 10. Since biomass fuel has a large impact on the combustion state of the boiler 200, when there are one or more mills 10 to which biomass fuel is supplied (when the number of mill control modes corresponding to biomass fuel set is one or more), a boiler control mode corresponding to biomass fuel is set, and the boiler 200 is controlled based on this boiler control mode.

Biomass fuel has a significant impact on the combustion state of the boiler 200. Therefore, when even one mill 10 is supplied with biomass fuel, the characteristics of the biomass fuel become dominant in the combustion state inside the furnace of the boiler 200. Therefore, the boiler control mode can be switched appropriately using the above processing.

Next, an example of control processing by the above-mentioned operation control system 80 will be described with reference to Figure 4. Figure 4 is a flowchart showing an example of the control processing procedure according to this embodiment. The flow in Figure 4 is repeatedly executed at a predetermined control cycle while the mill 10 and boiler 200 are in operation. The mill control mode of each mill 10 is set by the operator, and each mill 10 is controlled based on the set mill control mode.

First, the number of mills 10 supplied with each type of solid fuel is obtained (S101). S101 uses the mill control mode set for each mill 10, and is determined by the number of mill control modes set for each solid fuel.

Then, for each solid fuel, it is determined whether the number of mills 10 is equal to or greater than a threshold value set for the type of solid fuel (S102). Focusing on a specific solid fuel (predetermined solid fuel) in S102, it is determined whether the number of mills 10 to which the predetermined solid fuel is supplied is equal to or greater than a threshold value.

If the value is not greater than the threshold (NO in S102), the process ends. In other words, if the determination in S102 is NO, the boiler control mode remains unchanged.

If the value is above the threshold (YES in S102), the boiler control mode corresponding to the solid fuel that has exceeded the threshold is set. In other words, if the value is YES in S102, the boiler control mode is automatically changed from the originally set boiler control mode to the boiler control mode corresponding to the solid fuel that has exceeded the threshold.

Then, control of the boiler 200 is performed based on the set boiler control mode (S103). When the boiler control mode is changed, the control parameters are gradually changed as described above.

In this way, it is possible to link the mill control mode to automatically set the boiler control mode and perform boiler control.

In a method in which multiple types of fuel are pre-mixed and supplied to all mills 10 of the boiler 200 to achieve a mixed combustion state, if the fuel mixture ratio is changed, the combustion state of the boiler 200 changes depending on the mixture ratio. The boiler control mode for such a mixed combustion method can be achieved, for example, by proportionally allocating the control parameters set for each fuel according to the mixture ratio. On the other hand, in a method in which a single type of fuel is supplied to each mill 10 to achieve a mixed combustion state in the boiler 200 furnace, if the type of fuel is switched, the combustion state of the boiler 200 will be dominated by either the characteristics of the fuel before the switch or the characteristics of the fuel after the switch. In other words, the combustion state of the boiler 200 changes significantly in a short period of time. For example, when switching from bituminous coal to subbituminous coal as described above, the combustion state of the boiler 200 transitions from a state dominated by bituminous coal to a state dominated by subbituminous coal, with the threshold (majority) as the boundary. Therefore, by switching the boiler control mode using the number of mills 10 as a threshold, it is possible to select and control the appropriate boiler control mode according to the combustion state of the boiler 200.

An example of control of the mill 10 by the operation control system 80 will be described.
For example, a drive command is transmitted to the mill motor 15 to control the rotation speed of the grinding table 12 .
In addition, for example, a drive command is transmitted to the classifier motor 18 to control the rotation speed of the rotary classifier 16, thereby adjusting the classification performance, and the particle size of the pulverized fuel is maintained within a range that does not affect the combustibility of the solid fuel in the burner 220, while an amount of pulverized fuel corresponding to the amount of solid fuel supplied to the mill 10 is stably supplied to the burner 220.
In addition, for example, by transmitting a drive command to the coal feeder motor 27, the amount of solid fuel supplied to the mill 10 (amount of coal supply) is adjusted.
Furthermore, for example, by transmitting an opening command to the blower 30, the opening of the hot gas damper 30c and the cold gas damper 30d is controlled to adjust the flow rate and temperature of the primary air. Specifically, the opening of the hot gas damper 30c and the cold gas damper 30d is controlled so that the flow rate of the primary air supplied to the inside of the housing 11 and the temperature of the primary air at the outlet port 19 (mill outlet primary air temperature) become predetermined values set corresponding to the coal feed amount for each type of solid fuel. Note that the temperature of the primary air may also be controlled by controlling the temperature at the mill inlet (mill inlet primary air temperature).

As described above, the operation control system, power generation plant, operation control method, and operation control program of this embodiment allow for, when the mills 10 are controlled in a mill control mode corresponding to the supplied solid fuel, if the number of mills 10 supplied with a specific solid fuel reaches or exceeds a threshold value, the boiler control mode corresponding to this specific solid fuel is set to control the boiler 200. This makes it possible to appropriately set the boiler control mode according to the solid fuel being used.

When the specified solid fuel is coal (bituminous coal or sub-bituminous coal), by setting the threshold value as the majority of the operating mills 10, it is assumed that the conditions inside the boiler 200 furnace will be governed by the characteristics of the specified solid fuel, making it possible to appropriately set the boiler control mode in accordance with the specified solid fuel.

When the specified solid fuel is biomass fuel, by setting the threshold to one unit, it is assumed that the condition inside the boiler 200 furnace will be dominated by the characteristics of the specified solid fuel, making it possible to appropriately set the boiler control mode in accordance with the specified solid fuel.

By setting the control parameters of the mill 10 according to the mill control mode and the control parameters of the boiler 200 according to the boiler control mode, efficient control can be performed according to the set mode. When switching boiler control modes, changing the control parameters of the boiler 200 over a predetermined period of time prevents abrupt changes in the operating state of the boiler 200 (particularly the combustion state inside the furnace).

This disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the invention.

The operation control system and power plant, operation control method, and operation control program described in each of the above-described embodiments can be understood, for example, as follows.
The operation control system (80) according to the present disclosure is an operation control system (80) for a power plant equipped with a boiler (200) and a plurality of pulverizing units (10), and includes a pulverizing control unit (81) that controls the pulverizing units (10) based on a pulverizing control mode set for each pulverizing unit (10) depending on the fuel supplied, a mode setting unit (82) that sets a boiler control mode corresponding to a specified fuel when the number of pulverizing units (10) supplied with the specified fuel becomes equal to or greater than a threshold, and a boiler control unit (83) that controls the boiler (200) based on the boiler control mode.

According to the operation control system (80) disclosed herein, when the pulverizers (10) are controlled in a pulverization control mode corresponding to the supplied fuel, if the number of pulverizers (10) supplied with a specific fuel exceeds a threshold value, the boiler control mode corresponding to the specific fuel is set to control the boiler (200). This makes it possible to appropriately set the pulverizer control mode and boiler control mode according to the fuel being used.

In the operation control system (80) disclosed herein, the threshold value may be set corresponding to each of a plurality of specified fuels.

The operation control system (80) disclosed herein makes it possible to set boiler control modes corresponding to multiple fuels.

In the operation control system (80) according to the present disclosure, the mode setting unit (82) may use the set number of the pulverization control modes corresponding to the specified fuel as the number of pulverization units (10) to which the specified fuel is supplied.

The operation control system (80) disclosed herein makes it possible to easily determine the number of pulverizers (10) to which a given fuel is supplied by using the number of pulverizer control modes set for a given fuel.

In the operation control system (80) disclosed herein, the threshold value may be set as the majority of the pulverization during operation when the specified fuel is coal.

According to the operation control system (80) disclosed herein, when the specified fuel is coal, the threshold value is set to the majority of the pulverized fuel during operation, and since it is assumed that the state inside the furnace of the boiler (200) is governed by the characteristics of the specified fuel, it is possible to appropriately set the boiler control mode in accordance with the specified fuel.

In the operation control system (80) disclosed herein, the threshold value may be set to 1 when the specified fuel is biomass fuel.

According to the operation control system (80) disclosed herein, when the specified fuel is biomass fuel, by setting the threshold to one, it is assumed that the state inside the furnace of the boiler (200) will be governed by the characteristics of the specified fuel, and therefore it is possible to appropriately set the control mode (200) corresponding to the specified fuel.

In the operation control system (80) according to the present disclosure, the threshold value may be set to a smaller number of values for fuels that have a greater impact on the operation of the boiler (200).

According to the operation control system (80) disclosed herein, even if a fuel that has a high impact on the operation of the boiler (200) uses a small number of pulverizers, the state inside the furnace of the boiler (200) is expected to be dominated by the characteristics of this fuel. Therefore, by setting a threshold value for a smaller number of pulverizers for fuels with a higher impact, it is possible to appropriately set the boiler control mode.

In the operation control system (80) according to the present disclosure, the pulverization control unit (81) may control the pulverization based on control parameters of the pulverization unit (10) associated with the pulverization control mode, and the boiler control unit (83) may control the boiler (200) based on control parameters of the boiler (200) associated with the boiler control mode.

The operation control system (80) disclosed herein sets control parameters for the pulverizer (10) in accordance with the pulverization control mode, and sets control parameters for the boiler (200) in accordance with the boiler control mode, thereby enabling efficient control in accordance with the set mode.

In the operation control system (80) according to the present disclosure, when switching the boiler control mode, the boiler control unit (83) may change the control parameters of the boiler (200) over a predetermined time period to change the operating state of the boiler (200).

According to the operation control system (80) disclosed herein, when switching the boiler control mode, the control parameters of the boiler (200) are changed over a predetermined period of time, thereby preventing the operating state of the boiler (200) (particularly the combustion state inside the furnace) from suddenly changing and becoming unstable.

The power generation plant (1) according to the present disclosure comprises a boiler (200), multiple grinding sections (10), and the above-described operation control system (80).

The operation control method disclosed herein is an operation control method for a power plant equipped with a boiler (200) and multiple pulverizers (10), and includes a pulverizer control step for controlling the pulverizers (10) based on a pulverizer control mode set for each pulverizer (10) depending on the fuel supplied; a mode setting step for setting a boiler control mode corresponding to a specified fuel when the number of pulverizers supplied with the specified fuel exceeds a threshold; and a boiler control step for controlling the boiler (200) based on the boiler control mode.

The operation control program disclosed herein is an operation control program for a power plant equipped with a boiler (200) and multiple pulverizers (10), and causes a computer to execute a pulverizer control process that controls the pulverizers (10) based on a pulverizer control mode set for each pulverizer (10) depending on the fuel supplied; a mode setting process that sets a boiler control mode corresponding to a specified fuel when the number of pulverizers supplied with the specified fuel exceeds a threshold; and a boiler control process that controls the boiler (200) based on the boiler control mode.

1: Power plant 10: Mill (grinding section)
11: Housing 12: Crushing table 13: Crushing roller 14: Reducer (drive transmission unit)
15: Mill motor (drive unit)
16: Rotary classifier (classifying section)
16a: Blade 17: Coal feed pipe (fuel supply section)
18: Classifier motor 19: Outlet port 21: Bunker (storage section)
22: Downspout portion 25: Coal feeder (fuel feeder)
26: Conveying section 27: Coal feeder motor 30: Blower section (carrier gas supply section)
30a: Hot gas flow path 30b: Cold gas flow path 30c: Hot gas damper 30d: Cold gas damper 31: Primary air ventilator (PAF)
32: Forced draft fan (FDF)
33: Induced draft fan (IDF)
34: Air preheater (heat exchanger)
40: Status detection unit (temperature detection means, differential pressure detection means)
41: Bottom surface portion 42: Ceiling portion 45: Journal head 46: Pressing device (crushing load applying portion)
47: Support arm 48: Support shaft 80: Operation control system 81: Mill control unit 82: Mode setting unit 83: Boiler control unit 100: Solid fuel pulverizer 110: Primary air flow path (carrier gas flow path)
120: Pulverized fuel supply passage (pulverized fuel supply pipe)
200: Boiler 210: Furnace 220: Burner (combustion device)
1100: CPU
1200: Main memory 1300: Storage unit 1400: External interface 1500: Communication interface 1600: Input unit 1700: Display unit

Claims (10)

An operation control system for a power plant including a boiler and a plurality of grinding units,
a pulverization control unit that controls the pulverization units based on a pulverization control mode set for each pulverization unit in accordance with the supplied fuel;
a mode setting unit that sets a boiler control mode corresponding to the predetermined fuel when the number of the pulverizers to which the predetermined fuel is supplied becomes equal to or greater than a threshold value;
a boiler control unit that controls the boiler based on the boiler control mode;
Equipped with
An operation control system in which the threshold value is set to a smaller number for a fuel that has a greater impact on the operation of the boiler . The operation control system described in claim 1, wherein the threshold value is set corresponding to each of a plurality of specified fuels. The operation control system described in claim 1 or 2, wherein the mode setting unit uses the set number of the pulverization control mode corresponding to the specified fuel as the number of pulverization units to which the specified fuel is supplied. An operation control system described in any one of claims 1 to 3, wherein the threshold value is set as the majority of the pulverizers in operation when the specified fuel is coal. An operation control system according to any one of claims 1 to 4, wherein the threshold value is set to 1 when the specified fuel is biomass fuel. the pulverization control unit controls the pulverization unit based on a control parameter of the pulverization unit associated with the pulverization control mode,
The operation control system according to claim 1 , wherein the boiler control unit controls the boiler based on a control parameter of the boiler associated with the boiler control mode. The operation control system according to claim 6 , wherein the boiler control unit, when switching the boiler control mode, changes the control parameters of the boiler over a predetermined time period to change the operating state of the boiler . The boiler;
The plurality of crushing units;
An operation control system according to any one of claims 1 to 7 ;
A power plant comprising: An operation control method for a power plant including a boiler and a plurality of grinding units, comprising:
a pulverization control step of controlling the pulverization units based on a pulverization control mode set for each pulverization unit in accordance with the supplied fuel;
a mode setting step of setting a boiler control mode corresponding to the predetermined fuel when the number of the pulverizers to which the predetermined fuel is supplied becomes equal to or greater than a threshold value;
a boiler control step of controlling the boiler based on the boiler control mode;
and
The threshold value is set to a smaller value for the fuel that has a greater impact on the operation of the boiler . An operation control program for a power plant including a boiler and a plurality of grinding units,
a crushing control process for controlling the crushing units based on a crushing control mode set for each crushing unit in accordance with the supplied fuel;
a mode setting process for setting a boiler control mode corresponding to a predetermined fuel when the number of the pulverizers supplied with the predetermined fuel is equal to or greater than a threshold value, which is set so that the number of pulverizers is smaller for fuels that have a greater impact on the operation of the boiler;
a boiler control process for controlling the boiler based on the boiler control mode;
An operation control program that causes a computer to execute the above.