Plant control device, power generation plant, plant control method, and plant control program

Abstract

To provide a plant control device, a power generation plant, a plant control method, and a plant control program, which are improved in load following capability.SOLUTION: A plant control device 50 controls a power generation plant 1 that comprises a solid fuel pulverization device 100 for pulverizing solid fuel to produce pulverized fuel, and a boiler 200 for generating steam by burning the pulverized fuel supplied from the solid fuel pulverization device 100. The power generation plant 1 generates electric power according to the system frequency of a power supply system, and corrects the droop bias applied to the governor valve opening command of a turbine that is driven by the main steam pressure of the boiler 200, according to an actual governor valve opening command that indicates the characteristics of an actual governor valve obtained in advance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a plant control device, a power generation plant, a plant control method, and a plant control program. [Background technology]

[0002] Large boilers, such as power generation boilers, have a hollow furnace installed vertically, with multiple burners arranged circumferentially around the furnace wall. Large boilers also have a flue connected vertically above the furnace, with a heat exchanger for generating steam located in the flue. The burner injects a mixture of fuel and air (oxidizing gas) into the furnace, forming a flame, generating combustion gas that flows down the flue. A heat exchanger is installed in the area where the combustion gas flows, and superheated steam is generated by heating water or steam flowing through the heat transfer tubes that make up the heat exchanger.

[0003] Conventionally, solid fuels such as biomass fuels and coal are pulverized into fine powder within a predetermined particle size range in a pulverizer (mill) and then supplied to a combustion device. In the mill, the solid fuel fed onto the pulverizing table is pinched between the pulverizing table and pulverizing rollers to pulverize it. The pulverized solid fuel is then sorted into fine particles within a predetermined particle size range using a classifier. The fine particles are then transported to a boiler by a carrier gas (primary air) supplied from the periphery of the pulverizing table and combusted in the combustion device. In a thermal power plant, steam is generated by heat exchange between the combustion gas produced by burning the pulverized fuel in the boiler and feedwater. This steam drives a steam turbine, which in turn drives a generator connected to the steam turbine, thereby generating electricity.

[0004] In recent years, the amount of electricity generated from renewable energy sources has been increasing in light of the need for carbon neutrality. However, renewable energy power generation faces challenges in terms of stable power supply, and there are cases where a gap exists between electricity demand and the amount of electricity generated from renewable energy sources. Thermal power generation, particularly coal-fired power generation, is being called upon to shift from its traditional baseload operation to an operation used to adjust to fill the gap between electricity demand and the amount of electricity generated from renewable energy sources. This may require coal-fired power generation facilities to have frequency response capabilities that exceed the normal rate of load change. Since coal-fired power generation facilities are not as fast in load following as, for example, gas turbine power generation facilities, improvements in load following are being considered. For example, Patent Document 1 discloses that in a boiler, a droop bias is applied to a governor valve opening command, which is an opening command for a main steam control valve (governor valve). Furthermore, Patent Document 2 discloses that a pulverizer (mill) outputs a rotation speed command for a classifier in accordance with the contents of a frequency control command. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-82701 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-254930 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the invention of Patent Document 1, the droop bias is simply applied to the governor valve position command, and there are cases where the actual governor valve operation cannot adapt to the ideal governor valve characteristics due to, for example, aging of the governor valve. Furthermore, in the invention of Patent Document 2, each function is simply applied to the amount of coal fed, and it may take time for the rotation speed command for the classifier to change after the amount of coal fed changes.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a plant control device, a power generation plant, a plant control method, and a plant control program with improved load following capability. [Means for solving the problem]

[0008] In order to solve the above problems, the plant control device, power generation plant, plant control method, and plant control program of the present disclosure employ the following means. The plant control device disclosed herein is a plant control device that controls a power generation plant that includes a solid fuel pulverizer that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, and the power generation plant generates electricity according to the system frequency of a power supply system, and corrects a droop bias applied to a governor valve opening command of a turbine driven by the main steam pressure of the boiler according to an actual governor valve opening command that indicates the characteristics of the actual governor valve obtained in advance.

[0009] The plant control device disclosed herein is a plant control device that controls a power generation plant that includes a solid fuel pulverizer that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, and the power generation plant generates electricity according to the system frequency of a power supply system, and when the system frequency increases, it issues a rotation speed command to increase the rotation speed of the classifier of the solid fuel pulverizer, and when the system frequency decreases, it issues a rotation speed command to decrease the rotation speed of the classifier of the solid fuel pulverizer.

[0010] The plant control device disclosed herein is a plant control device that controls a power generation plant that includes a solid fuel pulverizer that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, and the power generation plant generates electricity according to the system frequency of a power supply system, and corrects the air flow rate supplied to the solid fuel pulverizer based on the rate of change of the solid fuel supply amount according to the system frequency.

[0011] The power generation plant of the present disclosure includes a solid fuel pulverizer that pulverizes solid fuel to produce pulverized fuel, a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, and any of the plant control devices described above.

[0012] The plant control method disclosed herein is a plant control method for controlling a power generation plant including a solid fuel pulverization device that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverization device, wherein the power generation plant generates electricity in accordance with the system frequency of a power supply system, and includes a step of correcting a droop bias applied to a governor valve position command of a turbine driven by the main steam pressure of the boiler in accordance with an actual governor valve position command that indicates actual governor valve characteristics obtained in advance, the step being executed by a computer.

[0013] The plant control method disclosed herein is a plant control device that controls a power generation plant that includes a solid fuel pulverizer that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, wherein the power generation plant generates electricity according to the system frequency of a power supply system, and includes the steps of issuing a rotation speed command to increase the rotation speed of a classifier of the solid fuel pulverizer when the system frequency increases, and issuing a rotation speed command to decrease the rotation speed of the classifier of the solid fuel pulverizer when the system frequency decreases, and is executed by a computer.

[0014] The plant control method disclosed herein is a plant control method for controlling a power generation plant that includes a solid fuel pulverization device that pulverizes solid fuel to produce pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverization device, wherein the power generation plant generates electricity according to the system frequency of a power supply system, and includes a step of issuing a command to the air flow rate supplied by the carrier gas supply unit of the solid fuel pulverization device based on the solid fuel supply amount according to the system frequency, and the step is executed by a computer.

[0015] A plant control program according to the present disclosure causes a computer to execute any one of the plant control methods described above. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to improve the response speed of a power plant to fluctuations in system frequency and perform load control while suppressing excessive fluctuations in the main steam pressure of a boiler. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram illustrating a boiler that uses solid fuel as a primary fuel in some embodiments of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram illustrating a heat exchanger in a coal-fired boiler according to some embodiments of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram illustrating a solid fuel comminution device according to some embodiments of the present disclosure. [Figure 4] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to some embodiments of the present disclosure. [Figure 5] FIG. 1 is a diagram illustrating a conventional droop bias relative to a grid frequency. [Figure 6] FIG. 10 is a diagram illustrating a generator output relative to a governor valve position command in some embodiments of the present disclosure. [Figure 7] FIG. 1 illustrates a circuit for performing correction according to governor valve characteristics in some embodiments of the present disclosure. [Figure 8]FIG. 10 is a diagram illustrating a droop bias with respect to a system frequency when correction is performed using an actual governor valve position command in some embodiments of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating a droop bias with respect to a system frequency when correction is performed using an actual governor valve position command in some embodiments of the present disclosure. [Figure 10] FIG. 10 illustrates a circuit for adjusting the rotation speed of a classifier in some embodiments of the present disclosure. [Figure 11] FIG. 1 illustrates a circuit for adjusting the air flow rate supplied to a boiler in some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of a plant control device, a power generation plant, a plant control method, and a plant control program according to the present disclosure will be described with reference to the drawings. An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

[0019] FIG. 1 is a schematic diagram illustrating a boiler that uses solid fuel as its main fuel according to some embodiments of the present disclosure.

[0020] The boiler 200 of this embodiment is a boiler that can generate superheated steam by burning pulverized fuel made by pulverizing solid fuel with a burner and exchanging the heat generated by this combustion with feedwater or steam. Biomass fuel, coal, etc. are used as solid fuel.

[0021] The boiler 200 has a furnace 210, a combustion device 202, and a combustion gas passage 212. The furnace 210 has a hollow rectangular cylindrical shape and is installed vertically. The furnace wall 101 that forms the inner wall surface of the furnace 210 is composed of multiple heat transfer tubes and fins that connect the heat transfer tubes together, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with water and steam circulating inside the heat transfer tubes, while suppressing the temperature rise of the furnace wall 101.

[0022] The combustion device 202 is installed in the lower region of the furnace 210. In this embodiment, the combustion device 202 has a plurality of burners 220A, 220B, 220C, 220D, 220E, and 220F (hereinafter, they may be collectively referred to as "burners 220") attached to the furnace wall 101. The burners 220 are arranged in multiple vertical rows, with each set consisting of burners evenly spaced along the circumferential direction of the furnace 210 (for example, four burners installed at each corner of the rectangular furnace 210). For convenience of illustration, only two burners from one set are shown in FIG. 1, and each set is denoted by the reference numerals 220A, 220B, 220C, 220D, 220E, and 220F. The shape of the furnace 210, the number of burner rows, the number of burners per row, and the arrangement of the burners are not limited to this embodiment.

[0023] The burners 220A, 220B, 220C, 220D, 220E, and 220F are connected to a plurality of mills (pulverizers) 10A, 10B, 10C, 10D, 10E, and 10F (hereinafter, sometimes collectively referred to as "mills 10") via a plurality of pulverized fuel supply pipes 120A, 120B, 120C, 120D, 120E, and 120F (hereinafter, sometimes collectively referred to as "pulverized fuel supply pipes 120"). The mill 10 is, for example, a vertical roller mill having a rotatable grinding table (not shown) supported therein and a plurality of grinding rollers (not shown) supported above the grinding table so that they can rotate in conjunction with the rotation of the grinding table. The solid fuel pulverized by the cooperation of the grinding rollers and the grinding table is transported to a classifier (not shown) provided in the mill 10 by primary air (carrier gas, oxidizing gas) supplied to the mill 10. The classifier separates the pulverized fuel into pulverized fuel with a particle size smaller than that suitable for combustion in the burner 220 and coarse pulverized fuel with a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 220 together with primary air via the pulverized fuel supply pipe 120. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 10 under its own weight and is re-ground.

[0024] An air register 230 is provided outside the furnace 210 at the installation position of the burner 220, and one end of an air duct (air duct) 240 is connected to the air register 230. A forced draft fan (FDF) 32 is connected to the other end of the air duct 240. The air supplied from the forced draft fan 32 is heated by an air preheater 34 installed in the air duct 240 (details will be described later), and is supplied to the burner 220 via the air register 230 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 210.

[0025] The combustion gas passage 212 is connected to the vertical upper part of the furnace 210. The combustion gas passage 212 is provided with superheaters 102A, 102B, and 102C (hereinafter sometimes collectively referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter sometimes collectively referred to as "reheaters 103"), and a coal economizer 104 as heat exchangers for recovering heat from the combustion gas, and heat is exchanged between the combustion gas generated in the furnace 210 and feedwater or steam circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to those shown in FIG. 1.

[0026] A flue 213 is connected to the downstream side of the combustion gas passage 212, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 34 is provided between the flue 213 and the air duct 240, and heat is exchanged between the air flowing through the air duct 240 and the combustion gas flowing through the flue 213, and the primary air supplied to the mill 10 and the secondary air supplied to the burner 220 are heated, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

[0027] Furthermore, a denitration device 35 may be provided in the flue 213 at a position upstream of the air preheater 34. The denitration device 35 supplies a reducing agent, such as ammonia or urea water, that has the effect of reducing nitrogen oxides to the combustion gas flowing through the flue 213, and promotes the reaction between the nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst provided in the denitration device 35, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 36 is connected to the flue 213 downstream of the air preheater 34. The gas duct 36 is provided with environmental equipment such as a dust collector 37, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, and a desulfurization equipment 38 that removes sulfur oxides, as well as an induced draft fan (IDF) 33 that guides the exhaust gas to these environmental equipment. The downstream end of the gas duct 36 is connected to a chimney 39, and the combustion gas that has been treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0028] In the boiler 200, when the multiple mills 10 are driven, pulverized and classified pulverized fuel is supplied to the burner 220 together with primary air via the pulverized fuel supply pipe 120. In addition, secondary air heated by the air preheater 34 is supplied to the burner 220 from the air duct 240 through the wind box 230. The burner 220 blows a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 210, and also blows secondary air into the furnace 210. The pulverized fuel mixture blown into the furnace 210 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 210, and high-temperature combustion gas rises within the furnace 210 and flows into the combustion gas passage 212. In this embodiment, air is used as the oxidizing gas (primary air, secondary air), but the oxidizing gas may have a higher or lower oxygen content than air, and stable combustion can be achieved in the furnace 210 by adjusting the ratio of the amount of oxygen to the amount of fuel supplied within an appropriate range.

[0029] Additionally, above the mounting position of the burner 220 of the furnace 210, a plurality of additional air ports (AA ports) 250 for supplying additional air for combustion (AA) into the furnace 210 are provided. The additional air ports 250 are connected to the ends of additional air ducts (AA ducts) 260 branching off from the air duct 240, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 250 via the additional air ducts 260 as additional air for combustion.

[0030] In region A (corresponding to the installation range of the wind box 230 in the height direction) inside the furnace 210 shown in Fig. 1, a flame is formed by combustion of a mixture of primary air and pulverized fuel with secondary air. Here, the air ratio in region A is set to be 1 or less, specifically, the amount of air supplied to the burner 220 (the total amount of primary air and secondary air) is set to be less than the theoretical amount of air relative to the amount of fuel supplied to the burner 220. By doing so, regions A and B (regions between the top of the burner 220 and the bottom of the additional air port 250) inside the furnace 210 become reducing atmospheres, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 210. Thereafter, in region C (region above the bottom of the additional air port 250), additional combustion air is supplied from the additional air port 250 to the combustion gas in which NOx has been reduced, completing the combustion. However, the amount of NOx generated is reduced by the reduction effect in regions A and B.

[0031] The combustion gas that has flowed into the combustion gas passage 212 exchanges heat with water and steam in the superheater 102, reheater 103, and economizer 104 arranged inside the combustion gas passage 212, and is then discharged into the flue 213, where nitrogen oxides are removed in the denitration device 35, and the gas exchanges heat with primary air and secondary air in the air preheater 34. The combustion gas is then discharged into the gas duct 36, where ash and the like are removed in the dust collector 37, and sulfur oxides are removed in the desulfurization device 38, and the gas is then discharged to the outside of the system through the chimney 39. Note that the arrangement of the heat exchangers in the combustion gas passage 212 and the arrangement of the devices from the flue 213 to the gas duct 36 with respect to the combustion gas flow do not necessarily have to be in the order described above.

[0032] Next, a detailed description will be given of the heat exchangers, namely, the superheater 102, the reheater 103, and the economizer 104, which are provided in the combustion gas passage 212. Fig. 2 is a schematic diagram showing heat exchangers provided in a coal-fired boiler according to some embodiments of the present disclosure. Note that Figure 1 does not accurately show the positions of the heat exchangers (superheaters 102A, 102B, 102C, reheaters 103A, 103B, and economizer 104) in the combustion gas passage 212, and the arrangement order of the heat exchangers relative to the combustion gas flow is not limited to that shown in Figure 1.

[0033] 2, the power plant 1 of this embodiment includes a heat exchanger provided in a boiler 200, a steam turbine 111 that is rotationally driven by steam generated in the boiler 200, and a generator 113 that is connected to the steam turbine 111 and generates electricity using the rotational force of the steam turbine 111. The electricity generated by the generator 113 is supplied to a power supply system (not shown).

[0034] The steam turbine 111, which is rotationally driven by steam generated in the boiler 200, is composed of, for example, a high-pressure turbine 111A, an intermediate-pressure turbine 111B, and a low-pressure turbine 111C. Steam heated in a superheater 102 of the boiler 200 drives the high-pressure turbine 111A, is then reheated in a reheater 103 of the boiler 200, and drives the intermediate-pressure turbine 111B and the low-pressure turbine 111C. A condenser 112 is connected to the low-pressure turbine 111C, and the steam that has driven the low-pressure turbine 111C is condensed into condensed water by heat exchange with cooling water (e.g., seawater or river water) in the condenser 112. The condenser 112 is connected to the economizer 104 via a water supply line L1. The feedwater line L1 is provided with, for example, a condensate pump (CP) 121, a low-pressure feedwater heater 122, a boiler feedwater pump (BFP) 123, and a high-pressure feedwater heater 124. A portion of the steam that drives the steam turbine 111 is extracted and supplied to the low-pressure feedwater heater 122 and the high-pressure feedwater heater 124 via an extraction line (not shown) as a heat source, and the feedwater that is supplied to the economizer 104 is heated.

[0035] For example, a case will be described in which the boiler 200 is a once-through boiler. The economizer 104 is connected to heat transfer tubes that constitute the furnace wall 101. The feedwater heated by the economizer 104 is heated by radiation from the flame in the furnace 210 as it passes through the heat transfer tubes that constitute the furnace wall 101, and is then led to the steam separator 125. The steam separated in the steam separator 125 is supplied to the superheater 102, and the drain water separated in the steam separator 125 flows into the steam separator drain tank 126 and is led to the condenser 112 via the drain water line L2.

[0036] When the combustion gas flows through the combustion gas passage 212, heat of the combustion gas is recovered by the superheater 102, the reheater 103, and the economizer 104. Meanwhile, feedwater supplied from the boiler feed pump (BFP) 123 is preheated by the economizer 104, and then heated to become steam while passing through the heat transfer tubes that make up the furnace wall 101, and is then guided to the steam separator 125. The steam separated in the steam separator 125 is introduced into the first superheater 102A, the second superheater 102B, and the third superheater 102C, where it is superheated by the combustion gas. The superheated steam generated in the superheater 102 is supplied to the high-pressure turbine 111A via the steam line L3, and rotates and drives the high-pressure turbine 111A. The steam discharged from the high-pressure turbine 111A is introduced into the first reheater 103A and the second reheater 103B, where it is superheated again. The re-superheated steam is supplied via steam line L5 to the low-pressure turbine 111C via the intermediate-pressure turbine 111B, and rotates the intermediate-pressure turbine 111B and the low-pressure turbine 111C. The rotating shaft of the steam turbine 111 rotates the generator 113, generating electricity. The steam discharged from the low-pressure turbine 111C is cooled in the condenser 112 to become condensed water, and is sent again to the economizer 104 via the water supply line L1.

[0037] 3 is a schematic diagram illustrating a solid fuel pulverizer according to some embodiments of the present disclosure. The power plant 1 according to this embodiment includes a solid fuel pulverizer 100 and a boiler 200.

[0038] The solid fuel pulverizer 100 of this embodiment is an apparatus that pulverizes solid fuel, such as biomass fuel or coal, to generate pulverized fuel and supply it to a burner 220 of a boiler 200, for example. The power plant 1 including the solid fuel pulverizer 100 and the boiler 200 shown in Figure 3 is equipped with one solid fuel pulverizer 100, but it may also be a system equipped with multiple solid fuel pulverizers 100 corresponding to each of the multiple burners 220 of one boiler 200.

[0039] The solid fuel pulverizing device 100 of this embodiment comprises a mill (pulverizing section) 10, a bunker (storage section) 21, a coal feeder (fuel supplying machine) 25, a blower section (carrier gas supplying section) 30, a status detection section 40, and a control device (plant control device) 50.

[0040] The mill 10 comprises 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 feed 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. It is arranged vertically at the center of the housing 11 and has its lower end extending into the interior of the housing 11.

[0041] 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 arranged. The grinding table 12 is a circular member in a plan view, and is arranged so that the lower end of the coal feed pipe 17 faces it. 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 bending upward. The coal feed pipe 17 supplies solid fuel (in this embodiment, for example, coal or biomass fuel) from above toward the grinding table 12 below, and the grinding table 12 sandwiches the supplied solid fuel between itself and the grinding rollers 13 and grinds it.

[0042] When solid fuel is fed from the coal feed pipe 17 toward the center of the pulverizing table 12, the centrifugal force generated by the rotation of the pulverizing table 12 guides the solid fuel toward the outer periphery of the pulverizing table 12, where it is pinched and pulverized between the pulverizing table 12 and the pulverizing rollers 13. The pulverized 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 given a 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. 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 mill 10 according to the present disclosure is a so-called pressurized mill in which pressurized primary air is blown into the mill 10 by the primary air ventilator 31 to dry the pulverized solid fuel while transporting it to the furnace 210. Therefore, the pressure inside the housing 11 is higher than the external (atmospheric) pressure.

[0043] 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. 3 shows only one representative crushing roller 13, but multiple 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 rotational axis of the crushing table 12.

[0044] The crushing roller 13 can be swung and displaced up and down by the journal head 45, and is supported so as to be able to move towards 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 the outer circumferential surface of the crushing roller 13 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.

[0045] 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 portion is horizontally aligned, allowing the crushing roller 13 to swing and displace up and down about the support shaft 48. A pressing device (crushing load applying unit) 46 is provided at the upper end portion 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 and the like 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).

[0046] The reducer 14 is connected to a 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.

[0047] 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 solid fuel pulverized by the pulverizing table 12 and 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 controlled by a control device 50, and rotates around a coal feed pipe 17, centered on a cylindrical axis (not shown) extending 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 instead of the blades 16a at the outer periphery of the casing.

[0048] 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 pulverizing table 12 to be pulverized again, and the fine pulverized fuel is led 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 together with the primary air from the outlet port 19 into the pulverized fuel supply flow path (pulverized fuel supply pipe) 120 and supplied to the burner 220 of the boiler 200.

[0049] The coal feed pipe 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, and supplies solid fuel fed from the top of the coal feed pipe 17 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 thereto.

[0050] 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 the 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 conveys the solid fuel discharged from the lower end of the downspout 22 to the upper part of the coal feed pipe 17 by the driving force of the coal feeder motor 27, and then deposits it inside. The amount of solid fuel supplied to the mill 10 is controlled by a signal from the control device 50, for example, by adjusting the movement speed of the belt conveyor of the conveying unit 26.

[0051] 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 the bunker 21. Inside the downspout section 22 that connects the bunker 21 and the coal feeder 25, fuel is layered. This solid fuel layer ensures a sealing property (material seal) that prevents the primary air and pulverized fuel from flowing back from the mill 10 toward the bunker 21.

[0052] 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 this embodiment, the blower section 30 is equipped with 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 order to appropriately adjust the flow rate and temperature of the primary air blown into the inside of the housing 11.

[0053] In this embodiment, the hot gas flow path 30a supplies a portion of the air sent out from the primary air fan 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 by the control device 50. 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.

[0054] 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 by the control device 50. 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.

[0055] 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 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, and is controlled by the control device 50. Furthermore, the oxygen concentration in the primary air blown from the primary air passage 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 passage 30a and mixing the same. By adjusting the oxygen concentration in the primary air, for example, when a highly ignitable (easily ignitable) 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.

[0056] In this embodiment, data measured or detected by the state detection unit 40 of the mill 10 is transmitted to the control device 50. The state detection unit 40 of this embodiment is, for example, a differential pressure measurement means, and measures the differential pressure of the mill 10 as the differential pressure between the pressure at the portion where primary air flows from the primary air flow path 110 into the inside of the housing 11 and the pressure at the outlet port 19 where the primary air and pulverized fuel are discharged from the inside of 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. In other words, by adjusting the rotation speed of the rotary classifier 16 according to 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, so that 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. Furthermore, 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, since the primary air is cooled inside the housing 11 by drying and transporting the pulverized fuel, 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.

[0057] The control device 50 is a device that controls each part of the solid fuel pulverizer 100. In the embodiment of the present disclosure, the control device 50 also controls each part of the boiler 200. The control device 50 may, for example, transmit a drive command to the mill motor 15 to control the rotation speed of the grinding table 12. The control device 50, for example, transmits a drive command to the classifier motor 18 to control the rotational speed of the rotary classifier 16 to adjust the classification performance, and can stably supply to the burner 220 an amount of pulverized fuel corresponding to the amount of solid fuel supplied to the mill 10 while maintaining the particle size of the pulverized fuel within a range that does not affect the combustibility of the solid fuel in the burner 220. Furthermore, the control device 50 can adjust the amount of solid fuel supplied to the mill 10 (amount of coal supply) by transmitting a drive command to the coal supply motor 27, for example. Furthermore, the control device 50 can adjust the flow rate and temperature of the primary air by controlling the opening rates of the hot gas damper 30c and the cold gas damper 30d by transmitting an opening rate instruction to the blower unit 30. Specifically, the control device 50 controls the opening rates of the hot gas damper 30c and the cold gas damper 30d 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 rate for each type of solid fuel. Note that the control of the primary air temperature may also be performed for the temperature at the mill inlet (mill inlet primary air temperature). Furthermore, the control device 50 can adjust the generator output in accordance with the power system frequency by adjusting an opening command that is an opening command for a governor valve (main steam control valve), for example.

[0058] FIG. 4 is a diagram illustrating an example of a hardware configuration of a control device according to some embodiments of the present disclosure. 4, the control device (Controller) 50 is a computer system that includes, for example, a CPU (Central Processing Unit: Processor) 1100, a secondary storage device (ROM, Secondary storage: Memory) 1300, a main storage device (RAM, Main Memory) 1200, a communication I / F 1400 for connecting to a network or the like, and an input / output unit 1500. These units are connected via a bus 1800.

[0059] The CPU 1100 controls the entire control device 50 using, for example, an OS (Operating System) stored in a secondary storage device 1300 connected via a bus 1800, and executes various processes by executing various programs stored in the secondary storage device 1300. One or more CPUs 1100 may be provided, and may implement processes in cooperation with each other.

[0060] The main memory device 1200 is composed of writable memory such as cache memory and RAM (Random Access Memory), and is used as a working area for reading out programs executed by the CPU 1100 and writing data processed by the programs.

[0061] The secondary storage device 1300 is a non-transitory computer-readable storage medium. Examples of the secondary storage device 1300 include a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, and a semiconductor memory. Examples of the secondary storage device 1300 include a read-only memory (ROM), a hard disk drive (HDD), and a solid-state drive (SSD) flash memory. The secondary storage device 1300 stores, for example, an operating system (OS) for controlling the entire information processing device, such as Windows (registered trademark), iOS (registered trademark), or Android (registered trademark), a basic input / output system (BIOS), various device drivers for operating peripheral devices, various application software, and various data and files. The secondary storage device 1300 also stores programs for implementing various processes and various data required for implementing the various processes. A plurality of secondary storage devices 1300 may be provided, and the above-described programs and data may be stored separately in each secondary storage device 1300.

[0062] A series of processes for realizing the functions of the control device 50 is stored in the secondary storage device 1300 or the like in the form of a program, for example, and the CPU (processor) 1100 reads this program into the main storage device 1200 and executes information processing and arithmetic processing to realize various functions. Note that the program may be pre-installed in the secondary storage device 1300, provided in a state stored in another non-transitory computer-readable storage medium, or distributed via wired or wireless communication means. Examples of non-transitory computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0063] Next, a brief explanation will be given again of the boiler 200 that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer 100. The boiler 200 includes a furnace 210 and a burner 220.

[0064] 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) sent out from a forced draft fan (FDF) 32 with 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, a superheater, and a coal economizer before being discharged to the outside of the boiler 200.

[0065] 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 then 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 to generate electricity, thereby constituting the power generation plant 1.

[0066] In a power system, the system frequency fluctuates due to changes in power demand. When power demand increases in a power system, the system frequency drops, and when power demand decreases, the system frequency rises. In response to these increases and decreases in system frequency, power generation facilities are required to respond at a rate of change that exceeds the normal load change rate (the rate of change when changing the amount of power generation).

[0067] Conventionally, a droop bias is applied to a governor valve opening command in corrective control of the turbine 111 in response to frequency fluctuations. The droop bias detects a turbine rotational speed deviation (rotational speed deviation) and applies a bias to the governor valve opening command to adjust the amount of steam supplied to the turbine 111. The amount of bias for the rotational speed deviation is determined by an arbitration rate (speed arbitration rate).

[0068] FIG. 5 is a diagram showing the droop bias relative to the conventional grid frequency. 5, the vertical axis represents the droop bias (arbitration rate), the horizontal axis represents the grid frequency, and the solid line represents the value of the droop bias relative to the grid frequency. In this embodiment, the droop bias is 100% when the grid frequency is −120 rpm, but these values are merely examples and will vary depending on the characteristics of the turbine 111.

[0069] As shown in FIG. 5, the conventional droop bias (mediation rate) is the same regardless of the governor valve responsiveness. Therefore, the governor valve responds with the same bias regardless of whether the governor valve is in a sensitive or sluggish responsiveness region, which may result in an inability to obtain the desired generator output. For example, in a sluggish responsiveness region, applying a conventional droop bias may cause a delay in response, making it impossible to obtain a generator output equivalent to the fluctuation in the grid frequency. Here, the governor valve responsiveness represents the governor valve's response performance to a governor valve position command. If the responsiveness is sensitive, the response of the opening to the position command will be fast, while if the responsiveness is sluggish, the response of the actual opening to the position command will be slow. Furthermore, depending on the governor valve, its responsiveness may have a tendency to change with respect to the position command. In this embodiment, the range of position commands in which the governor valve tends to be sensitive is referred to as the sensitive responsiveness region, and the range of position commands in which the governor valve tends to be sluggish is referred to as the sluggish responsiveness region.

[0070] FIG. 6 is a diagram illustrating a generator output relative to a governor valve opening command in some embodiments of the present disclosure. In FIG. 6, the vertical axis is the generator output, the horizontal axis is the governor valve opening command, the solid line is an example of the actual governor valve characteristics, and the dashed line is the ideal governor valve characteristics.

[0071] The conventional droop bias shown in Figure 5 assumes ideal governor valve characteristics, shown by the dashed line in Figure 6, in which generator output is proportional to the governor valve opening. However, actual governor valves each have their own characteristics, and in some cases, generator output is not proportional to the valve opening, unlike the ideal governor valve characteristics, as shown by the solid line in Figure 6. One possible reason that the actual governor valve characteristics deviate from the ideal governor valve characteristics is the deterioration of the governor valve over time.

[0072] The actual governor valve characteristics shown by the solid line in Fig. 6 indicate that in the region where the solid line slopes gently, the governor valve opening response to the governor valve command, and therefore the generator output responsiveness, is slow. Conversely, in the region where the solid line slopes steeply, the generator output responsiveness to the governor valve opening command is sensitive. In an embodiment of the present disclosure, such actual governor valve characteristics are acquired in advance and acquired as a function as an actual governor valve position command. The function may be set as a coefficient for the governor valve position, for example.

[0073] 7 is a diagram showing a circuit that performs correction control according to the governor valve characteristics in some embodiments of the present disclosure. The circuit enclosed by the dashed line is a circuit that is added to the conventional droop bias. The rotational speed deviation of the turbine 111 is input to calculate a droop bias 72. Meanwhile, a governor valve position command is input to a function unit 71, which calculates an actual governor valve position command. A multiplier 73 corrects the droop bias 72 using the actual governor valve position command.

[0074] Meanwhile, a turbine master signal used to control the turbine 111 is input to a governor system 74 and a load limiter system 76. The governor system 74 is a circuit related to the governor valve, and the load limiter system 76 is a circuit related to load limitation, but both may employ known configurations as appropriate, and detailed explanations thereof will be omitted here. A droop bias corrected by the actual governor valve position command is added to the output of the governor system 74 by an adder 75. The output of the load limiter system 76 and the output of the adder 75 are compared by a lower value selector 77, and the lower of the two is output as the corrected governor valve position command.

[0075] 8 and 9 are diagrams illustrating the droop bias with respect to the system frequency when correction is performed using an actual governor valve position command in some embodiments of the present disclosure. Figure 8 shows the correction in the region where the responsiveness of the generator output to the valve opening is sensitive in terms of the governor valve characteristics, and Figure 9 shows the correction in the region where the responsiveness of the generator output to the valve opening is slow in terms of the governor valve characteristics. 8 and 9, the vertical axis represents the droop bias (arbitration rate), the horizontal axis represents the system frequency, the solid lines represent the conventional droop bias relative to the system frequency, and the dashed lines represent the droop bias relative to the system frequency when correction is performed using an actual governor valve position command. In this embodiment, the conventional droop bias is 100% when the system frequency is -120 rpm, but these values are merely examples and vary depending on the characteristics of the turbine 111.

[0076] As shown in Fig. 8, when correction is made using the actual governor valve position command in the region of the governor valve characteristics where the generator output response is sensitive to the valve position, a droop bias with respect to the grid frequency shown by the dashed line is applied, which has a gentler slope than the conventional droop bias with respect to the grid frequency shown by the solid line. This results in a low gain in the region where the generator output response is sensitive to the governor valve position command.

[0077] On the other hand, as shown in Fig. 9, when correction is made using the actual governor valve position command in a region of the governor valve characteristics where the generator output is sluggish in response to the valve position, a droop bias with respect to the grid frequency shown by the dashed line is applied, which has a steeper slope than the conventional droop bias with respect to the grid frequency shown by the solid line. In this way, in a region where the generator output is sluggish in response to the actual governor valve position command, a correction is made to make the droop bias larger than in a region where the generator response is sensitive. This results in a high gain in a region where the generator output is sluggish in response to the governor valve position command.

[0078] In this way, the droop bias applied to the governor valve position command for the turbine 111 is corrected in accordance with the actual governor valve characteristics obtained in advance, so that the governor valve position can be adjusted based on the governor valve characteristics. By adjusting the governor valve position, the governor valve position can be adjusted in accordance with fluctuations in the system frequency, and load responsiveness according to the governor valve position can be obtained. Furthermore, the response speed of the power plant 1 to fluctuations in the system frequency can be improved, and load control can be performed while suppressing excessive fluctuations in the main steam pressure of the boiler 200.

[0079] To respond to fluctuations in the system frequency, the boiler 200 needs to ensure a corresponding main steam pressure. However, if the main steam pressure becomes unstable due to changes in the governor valve opening, the output of the generator 113 driven by the turbine 111 cannot be obtained at the desired value, and an appropriate frequency response cannot be achieved.

[0080] When the system frequency rises, surplus power is generated in the system, and control is performed to reduce the governor valve opening in order to lower the generator output. If the amount of steam supplied to the turbine 111 decreases due to the reduction in the governor valve opening, the main steam pressure increases. In this case, control is performed to maintain the main steam pressure constant, which may result in an increase in generator output.

[0081] On the other hand, when the system frequency drops, the system is short of power, so control is performed to increase the governor valve opening in order to increase the generator output. If the amount of steam supplied to the turbine 111 increases as a result of the increase in the governor valve opening, the main steam pressure may decrease, causing the override control function to operate. In this case, control is performed to maintain the main steam pressure constant, which may result in a decrease in generator output.

[0082] Therefore, in the embodiment of the present disclosure, in order to improve the responsiveness of the boiler 200, the rotation speed of the rotary classifier 16 of the mill 10 is adjusted to suppress fluctuations in the main steam pressure. FIG. 10 is a diagram illustrating a circuit for adjusting the rotation speed of the classifier in some embodiments of the present disclosure.

[0083] The rotation speed command that controls the rotation speed of the rotary classifier 16 is set based on the coal feed rate, which is the amount of solid fuel supplied to the mill 10. In the circuit of FIG. 10, the coal feed rate is input to a function unit 86, and a rotation speed command corresponding to the coal feed rate is output. An adder 83 adds a correction value corresponding to fluctuations in the system frequency. Here, the coal feed rate signal input to the circuit of FIG. 10 may be a coal feed rate command signal output from the control device 50 to the coal feeder 25, or it may be a coal feed rate feedback signal output from the coal feeder 25 to the control device 50.

[0084] When there is no fluctuation in the system frequency, "0%" is input to this circuit, and the output value of the function unit 86 is output as the rotation speed command of the rotary classifier 16 in the adder 83.

[0085] When the system frequency increases, the switch 81 is turned on. When the system frequency decreases, the switch 82 is turned on. Either the switch 81 or the switch 82 is turned on.

[0086] When switch 81 is turned ON, the system frequency is rising, so the governor valve is operated in the direction to reduce the generator output. At this time, a generator output setting in the direction to reduce the output is input to function unit 84. When the generator output setting is input, function unit 84 outputs a command to increase the rotation speed of rotary classifier 16 accordingly. In adder 83, the output value of function unit 84 is added to the output value of function unit 86, and the result is output as a rotation speed command for rotary classifier 16.

[0087] When the rotation speed of the rotary classifier 16 increases, the amount of pulverized fuel discharged from the rotary classifier 16 to the pulverized fuel supply pipe 120 from the outlet port 19 together with the primary air decreases. That is, the amount of pulverized fuel supplied to the boiler 200 decreases. In this way, by adjusting the amount of pulverized fuel supplied to the boiler 200, fluctuations in main steam pressure can be suppressed. In addition, since the rotation speed of the rotary classifier 16 provided upstream of the pulverized fuel supply passage (pulverized fuel supply pipe) 120 is adjusted by capturing changes in generator output from an increase in system frequency, the response speed of the pulverized fuel amount supplied from the mill 10 to the boiler 200 can be increased.

[0088] When switch 82 is turned ON, the system frequency is dropping, so the governor valve is operated in the direction to increase the generator output. At this time, a generator output setting in the direction to increase the output is input to function unit 85. When the generator output setting is input, function unit 85 outputs a command to decrease the rotation speed of rotary classifier 16 in accordance with this. In adder 83, the output value of function unit 85 is added to the output value of function unit 86, and the result is output as a rotation speed command for rotary classifier 16.

[0089] When the rotation speed of the rotary classifier 16 decreases, the amount of pulverized fuel discharged from the rotary classifier 16 to the pulverized fuel supply pipe 120 from the outlet port 19 together with the primary air increases. That is, the amount of pulverized fuel supplied to the boiler 200 increases. In this way, by adjusting the amount of pulverized fuel supplied to the boiler 200, fluctuations in main steam pressure can be suppressed. In addition, since the rotation speed of the rotary classifier 16 provided upstream of the pulverized fuel supply passage (pulverized fuel supply pipe) 120 is adjusted by detecting changes in generator output from a drop in system frequency, the response speed of the pulverized fuel amount supplied from the mill 10 to the boiler 200 can be increased.

[0090] In the embodiment of the present disclosure, in order to improve the responsiveness of the boiler 200, the flow rate of air supplied to the mill 10 is adjusted to suppress fluctuations in the main steam pressure. FIG. 11 is a diagram illustrating a circuit for adjusting the air flow rate supplied to the mill 10 in some embodiments of the present disclosure.

[0091] As described above, the flow rate of the air supplied to the mill 10 is determined by the opening degree of the hot gas damper 30c and the cold gas damper 30d. In the embodiment of the present disclosure, the hot gas damper 30c and the cold gas damper 30d are collectively referred to as dampers. By controlling the opening of the damper, the flow rate of air supplied to the mill 10 and carrying the pulverized fuel to the boiler 200 is adjusted.

[0092] The flow rate of air supplied to the mill 10 is set based on the coal feed rate, which is the amount of solid fuel supplied to the mill 10 . 11, the amount of coal feed is input to a function unit 95, and an air flow command corresponding to the amount of coal feed is output. The air flow command corresponding to the amount of coal feed is compared with the actual air flow rate by a comparator 91, and the difference is proportionally integrated by an adjuster (PI controller) 92, and is output as a damper opening command. The coal feed rate signal input to the circuit of Figure 11 may be a coal feed rate command signal output from the control device 50 to the coal feeder 25, or it may be a coal feed rate feedback signal output from the coal feeder 25 to the control device 50.

[0093] Here, the coal supply amount fluctuates depending on the system frequency. That is, when the system frequency rises, a surplus of power is generated in the system, and therefore control is performed to reduce the coal supply amount in order to lower the generator output. On the other hand, when the system frequency falls, a shortage of power is generated in the system, and therefore control is performed to increase the coal supply amount in order to raise the generator output. Such changes in the coal feed rate due to fluctuations in the system frequency are captured by the output of a differentiator 93, which inputs the coal feed rate. By differentiating the coal feed rate, the rate of change in the coal feed rate can be obtained, and this is added to an air flow command corresponding to the coal feed rate by an adder 94. The output value of the adder 94 is input to a comparator 91 as a corrected air flow command and compared with the actual air flow rate. The difference of the comparator 91 is proportionally integrated by an adjuster (PI controller) 92, and is output as a corrected damper opening command.

[0094] In this way, a damper opening command is issued to control the damper opening based on the coal feed rate, which changes due to fluctuations in the system frequency, and the air flow rate supplied to the mill 10 is adjusted, thereby adjusting the air flow rate that transports pulverized fuel to the boiler 200. For example, if there is a sudden change in the coal feed rate, a correction is made to increase the air flow rate, and the air flow rate supplied to the mill 10 is increased, and control is performed to reduce the solid fuel remaining inside the mill 10.

[0095] This allows the change in the coal supply rate due to fluctuations in the system frequency to be detected, and the opening of the dampers (hot gas damper 30c and cold gas damper 30d) provided upstream of the mill 10 to be adjusted to control the flow rate of the conveying air, thereby increasing the response speed of the amount of pulverized fuel supplied from the mill 10 to the boiler 200. Also, fluctuations in the main steam pressure can be suppressed.

[0096] <Additional Notes> The plant control device, the power generation plant, the plant control method, and the plant control program described in the above-described embodiments can be understood, for example, as follows.

[0097] A plant control device (50) according to a first aspect of the present disclosure is a plant control device (50) that controls a power plant (1) including a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), wherein the power plant (1) generates power in accordance with the system frequency of a power supply system, and corrects a droop bias applied to a governor valve position command of a turbine (111) driven by main steam pressure of the boiler (200) in accordance with an actual governor valve position command that indicates actual governor valve characteristics obtained in advance.

[0098] The droop bias applied to the turbine governor valve position command is corrected in accordance with the actual governor valve characteristics acquired in advance, making it possible to adjust the governor valve position based on the governor valve characteristics. By adjusting the governor valve position, the governor valve position can be adjusted in accordance with fluctuations in the system frequency, and load responsiveness according to the governor valve position can be obtained. Furthermore, the response speed of the power plant to fluctuations in the system frequency can be improved, and load control can be performed while suppressing excessive fluctuations in the main steam pressure of the boiler.

[0099] A plant control device (50) according to a second aspect of the present disclosure is a plant control device (50) that controls a power generation plant (1) that includes a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), wherein the power generation plant (1) generates power according to the system frequency of a power supply system, and when the system frequency increases, issues a rotation speed command to increase the rotation speed of a classifier (16) of the solid fuel pulverizer (100), and when the system frequency decreases, issues a rotation speed command to decrease the rotation speed of the classifier (16) of the solid fuel pulverizer (100).

[0100] This improves the power plant's response speed to fluctuations in system frequency and enables load control while suppressing excessive fluctuations in the boiler's main steam pressure. The rotation speed of the classifier in the solid fuel pulverizer can be increased or decreased in response to fluctuations in the system frequency, thereby suppressing fluctuations in main steam pressure.The rotation speed of the classifier installed upstream of the coal supply path is adjusted by detecting changes in generator output from fluctuations in the system frequency, thereby speeding up the response speed of the amount of solid fuel supplied from the solid fuel pulverizer to the boiler. For example, if the frequency increases, the power supply system will have excess power, so the governor valve operates to reduce the generator output. In this embodiment, the rotation speed of the classifier of the solid fuel pulverizer is increased to reduce the amount of pulverized fuel supplied to the boiler, thereby suppressing the supply of solid fuel to the furnace.

[0101] A plant control device (50) according to a third aspect of the present disclosure is a plant control device (50) that controls a power generation plant (1) that includes a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), wherein the power generation plant (1) generates power in accordance with the system frequency of a power supply system, and corrects the air flow rate supplied to the solid fuel pulverizer (100) based on the rate of change in the amount of solid fuel supplied in accordance with the system frequency.

[0102] This improves the power plant's response speed to fluctuations in system frequency and enables load control while suppressing excessive fluctuations in the boiler's main steam pressure. The air flow rate supplied to the solid fuel pulverizer is corrected based on the rate of change in the amount of solid fuel supplied according to the system frequency. By detecting changes in the amount of solid fuel supplied to the solid fuel pulverizer and adjusting the air flow rate supplied into the furnace, the response speed of the amount of solid fuel supplied from the solid fuel pulverizer to the boiler can be increased.

[0103] The plant control device (50) of a fourth aspect of the present disclosure may be configured in the first aspect to perform a correction such that the droop bias is larger in a region where the responsiveness of the generator output to the actual governor valve position command is slow than in a region where the responsiveness of the generator is sensitive.

[0104] Since the droop bias correction is changed according to the responsiveness of the generator output to the actual governor valve opening command, it is possible to adjust the governor valve opening taking into account the characteristics of the governor valve.

[0105] According to a fifth aspect of the present disclosure, in the plant control device (50) of the third aspect, the command for the air flow rate may be a command for opening a damper of the carrier gas supply part (30).

[0106] By adjusting the opening of the damper in the carrier gas supply section located upstream of the solid fuel pulverizer, the amount of air and the amount of solid fuel supplied from the solid fuel pulverizer to the boiler can be adjusted, thereby increasing the response speed.

[0107] A power plant (1) of a sixth aspect of the present disclosure includes a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), and the plant control device (50) of the first aspect.

[0108] A power plant (1) of a seventh aspect of the present disclosure includes a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), and the plant control device (50) of the second aspect.

[0109] The power plant (1) of the eighth aspect of the present disclosure includes a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), and the plant control device (50) of the third aspect.

[0110] A plant control method according to a ninth aspect of the present disclosure is a plant control method for controlling a power plant (1) including a solid fuel pulverization device (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverization device (100), wherein the power plant (1) generates power in accordance with the system frequency of a power supply system, and includes a step of correcting a droop bias applied to a governor valve position command of a turbine (111) driven by main steam pressure of the boiler (200) in accordance with an actual governor valve position command that indicates actual governor valve characteristics obtained in advance, and the method is executed by a computer.

[0111] A tenth aspect of the plant control method of the present disclosure is a plant control method (50) for controlling a power plant (1) including a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), wherein the power plant (1) generates power according to the system frequency of a power supply system, and includes the steps of issuing a rotation speed command to increase the rotation speed of a classifier (16) of the solid fuel pulverizer (100) when the system frequency increases, and issuing a rotation speed command to decrease the rotation speed of the classifier (16) of the solid fuel pulverizer (100) when the system frequency decreases, and is executed by a computer.

[0112] A plant control method according to an eleventh aspect of the present disclosure is a plant control method (50) for controlling a power plant (1) including a solid fuel pulverizer (100) that pulverizes solid fuel to produce pulverized fuel, and a boiler (200) that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer (100), wherein the power plant (1) generates electricity in accordance with the system frequency of a power supply system, and includes a step of issuing a command to the air flow rate supplied by a carrier gas supply unit (30) of the solid fuel pulverizer (100) based on the amount of solid fuel supplied in accordance with the system frequency, and the method is executed by a computer.

[0113] A plant control program according to a twelfth aspect of the present disclosure causes a computer to execute the plant control method according to the ninth aspect.

[0114] A plant control program according to a thirteenth aspect of the present disclosure causes a computer to execute the plant control method according to the tenth aspect.

[0115] A plant control program according to a fourteenth aspect of the present disclosure causes a computer to execute the plant control method according to the eleventh aspect.

[0116] The above-described embodiments can be combined as appropriate.

[0117] In the above-described embodiment, the boiler of the present disclosure has been described as a boiler that uses solid fuel as fuel, but the boiler fuel is not limited to solid fuel, and can also use petroleum fuels such as heavy oil, light oil, and heavy oil, industrial wastewater, liquid ammonia, etc. Also, gaseous fuels such as natural gas, various petroleum gases, by-product gases generated in steelmaking processes, hydrogen gas, and ammonia gas can also be used. Furthermore, the present invention can also be applied to a multi-fuel boiler that uses a combination of these various fuels.

[0118] The solid fuel used in the boiler is not limited to that disclosed herein, and may be coal, biomass fuel, petroleum coke (PC), etc. Furthermore, these solid fuels may be used in combination. [Explanation of symbols]

[0119] 1. Power Plant 10 Mill (crusher, crushing section) 11. Housing 12 Grinding Table 13 Crushing roller 14 Reducer (drive transmission part) 15 Mill motor (drive unit) 16 Rotary classifier (classifying section) 16a blade 17 Coal feed pipe (fuel supply section) 18 Classifier motor 19 Exit Port 21 Bunka (storage section) 22 Downspout 25 Coal feeding machine (fuel supply machine) 26 Conveyor 27 Coal feeder motor 30 Blower (Carrier Gas Supply) 30a Hot gas flow path 30b Cold gas flow path 30c Thermal Gas Damper 30d Cold Gas Damper 31 Primary Air Ventilator (PAF) 32 Forced draft fan (FDF) 33 Induced Draft Fan (IDF) 34 Air preheater 35 Denitration equipment 36 Gas Duct 37 Dust collection device 38 Desulfurization equipment 39 Chimney 40 Status detection unit (temperature detection means, differential pressure detection means) 41 Bottom part 42 Ceiling 45 Journal Head 46 Pressing device (crushing load applying part) 47 Support Arm 48 Support shaft 50 Control device (plant control device) 100 Solid fuel crusher 101 Furnace wall 102 Superheater 102A 1st superheater 102B 2nd superheater 102C 3rd superheater 103 Reheater 103A 1st reheater 103B 2nd reheater 104 Economizer 110 Primary air flow path (carrier gas flow path) 111 Steam turbine 111A high pressure turbine 111B Intermediate Pressure Turbine 111C low pressure turbine 112 Condenser 113 Generator 120 Pulverized fuel supply passage (pulverized fuel supply pipe) 121 Condensate pump (CP) 122 Low pressure water heater 123 Boiler Feed Pump (BFP) 124 High-pressure water heater 125 Brackish water separator 126 Steam separator drain tank 200 boiler 202 Combustion equipment 210 Furnace 212 Combustion gas passage 213 Flue 220 Burner 230 Air register 240 Air duct 250 Additional Air Port 260 Additional Air Duct L1 water supply line L2 drain water line L3~L5 steam lines 1100 CPU 1200 Main storage 1300 Secondary storage 1400 communication interface 1500 Input / output section 1800 Bus

Claims

1. A plant control device that controls a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, the power generation plant generates power in accordance with a system frequency of a power supply system, a plant control device that corrects a droop bias applied to a governor valve position command for a turbine driven by the main steam pressure of the boiler in accordance with an actual governor valve position command that indicates characteristics of an actual governor valve obtained in advance.

2. A plant control device that controls a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, the power generation plant generates power in accordance with a system frequency of a power supply system, When the system frequency increases, a rotation speed command is issued to increase the rotation speed of the classifier of the solid fuel pulverizer; a plant control device that issues a rotation speed command to reduce the rotation speed of the classifier of the solid fuel pulverizer when the system frequency decreases;

3. A plant control device that controls a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, the power generation plant generates power in accordance with a system frequency of a power supply system, a plant control device that corrects the flow rate of air supplied to the solid fuel pulverizer based on the rate of change in the amount of solid fuel supplied according to the system frequency;

4. 2. The plant control device according to claim 1, wherein the droop bias is corrected to be larger in a region where the responsiveness of the generator output to the actual governor valve opening command is slow than in a region where the responsiveness of the generator output is sensitive.

5. 4. The plant control device according to claim 3, wherein the command for the air flow rate is a command for opening a damper of a carrier gas supply unit.

6. a solid fuel pulverizer for pulverizing the solid fuel to generate finely divided fuel; a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer; The plant control device according to claim 1 ; A power plant comprising:

7. a solid fuel pulverizer for pulverizing the solid fuel to generate finely divided fuel; a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer; The plant control device according to claim 2; A power plant comprising:

8. a solid fuel pulverizer for pulverizing the solid fuel to generate finely divided fuel; a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer; The plant control device according to claim 3; A power plant comprising:

9. A plant control method for controlling a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, comprising: the power generation plant generates power in accordance with a system frequency of a power supply system, a step of correcting a droop bias applied to a governor valve position command for a turbine driven by main steam pressure of the boiler in accordance with an actual governor valve position command that indicates characteristics of an actual governor valve obtained in advance.

10. A plant control method for controlling a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, comprising: the power generation plant generates power in accordance with a system frequency of a power supply system, When the system frequency increases, issuing a rotation speed command to increase the rotation speed of the classifier of the solid fuel pulverizer; When the system frequency decreases, issuing a rotation speed command to reduce the rotation speed of the classifier of the solid fuel pulverizer; A computer-implemented plant control method comprising:

11. A plant control method for controlling a power generation plant including a solid fuel pulverizer that pulverizes solid fuel to generate pulverized fuel, and a boiler that generates steam by burning the pulverized fuel supplied from the solid fuel pulverizer, comprising: the power generation plant generates power in accordance with a system frequency of a power supply system, A computer-executed plant control method comprising the step of issuing a command for the flow rate of air supplied by a carrier gas supply unit of the solid fuel pulverizer based on the solid fuel supply amount corresponding to the system frequency.

12. A plant control program for causing a computer to execute the plant control method according to claim 9.

13. A plant control program for causing a computer to execute the plant control method according to claim 10.

14. A plant control program for causing a computer to execute the plant control method according to claim 11.

Images