Control device for boiler, boiler system comprising the same, control method for boiler and control program for boiler

Abstract

To provide a control device for a boiler capable of improving responsiveness of a supply water flow rate in a boiler during change in the load of the boiler, a boiler system comprising the control device, a control method for a boiler and a control program for a boiler.SOLUTION: A control device for a boiler comprises: an acquisition unit 210 that acquires a state parameter of fluid flowing through a water wall pipe whose flow rate changes in response to change in the load of a boiler; a calculation unit 211 that calculates the deviation between a planned value of the state parameter based on planned performance of the boiler and a current value of the state parameter acquired by the acquisition unit; and a control unit (212) that executes feedback control on a supply water flow rate of the boiler in accordance with the deviation, and, when the deviation is equal to or larger than a predetermined threshold, executes holding control to hold a command value of the supply water flow rate at a predetermined value instead of the feedback control.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a boiler control device, a boiler system including the same, a boiler control method, and a boiler control program. [Background technology]

[0002] Large boilers, such as power generation boilers, have a hollow furnace installed vertically, with multiple burners arranged 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 water or steam flowing through the heat exchanger is heated to generate superheated steam.

[0003] Patent Document 1 discloses that in feedback control of a boiler, when setting a fuel flow rate according to a main steam pressure deviation, the setting of the fuel flow rate is adjusted according to a main steam temperature deviation. Similarly, when setting a feedwater flow rate according to a main steam temperature deviation, the feedwater flow rate is set according to a main steam pressure deviation. In other words, the feedback control disclosed in Patent Document 1 discloses that the interference between the control systems for the main steam pressure and the main steam temperature is adjusted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-79006 Summary of the Invention [Problem to be solved by the invention]

[0005] In a boiler fired with solid fuels such as biomass or coal, it takes a certain amount of time from when the fuel is supplied from the fuel bunker to the mill until the solid fuel pulverized by the mill is fed into the boiler furnace. Therefore, compared to a boiler fired with gaseous or liquid fuel, it takes time to increase or decrease the amount of fuel fed to the boiler (the amount of heat input to the boiler). In other words, solid fuel boilers tend to have slower load responsiveness than boilers that use other types of fuel.

[0006] When a boiler load increases, the response speeds of the boiler's feedwater flow rate, fuel flow rate, and air flow rate all differ. For example, the feedwater flow rate can be adjusted to a predetermined level faster than the fuel flow rate. This causes the ratio between the feedwater flow rate and the fuel flow rate to become inappropriate, resulting in a temporary drop in the fluid (water) temperature at the outlet of the water wall tube that makes up the boiler's furnace wall. Furthermore, the temperature of the steam flowing into the superheater and reheater, which are located downstream of the furnace in the direction of the boiler's combustion gas flow, also drops. Conversely, when the boiler load decreases, the delayed response of the boiler heat input may cause the steam temperature at the superheater outlet to rise unexpectedly. For the reasons mentioned above, these tendencies are particularly pronounced in solid-fuel-fired boilers. Therefore, it is necessary to suppress the impact on the temperature characteristics when the boiler load changes and stabilize boiler control.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a boiler control device that can improve the load responsiveness of a boiler when the boiler load changes, a boiler system equipped with the same, a boiler control method, and a boiler control program. [Means for solving the problem]

[0008] A boiler control device according to one aspect of the present disclosure comprises an acquisition unit that acquires state parameters of a fluid flowing through a water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation unit that calculates the deviation between a planned value of the state parameter based on the planned performance of the boiler and the current value of the state parameter acquired by the acquisition unit; and a control unit that executes feedback control of the boiler feedwater flow rate in accordance with the deviation, and, if the deviation is equal to or greater than a predetermined threshold, executes holding control to hold the command value of the feedwater flow rate at a predetermined value instead of the feedback control.

[0009] A boiler system according to one aspect of the present disclosure includes a control device for the boiler, and a boiler that burns pulverized fuel made from pulverized solid fuel using a burner and exchanges the heat generated by this combustion with feedwater or steam to generate superheated steam.

[0010] A boiler control method according to one aspect of the present disclosure comprises an acquisition step of acquiring state parameters of a fluid flowing through a water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation step of calculating the deviation between a planned value of the state parameter based on the planned performance of the boiler and the current value of the state parameter acquired in the acquisition step; and a control step of executing feedback control regarding the boiler feedwater flow rate in accordance with the deviation, and, if the deviation is equal to or greater than a predetermined threshold, executing holding control to hold the command value of the feedwater flow rate at a predetermined value instead of the feedback control.

[0011] A boiler control program according to one aspect of the present disclosure causes a computer to function as any one of the boiler control devices described above. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a boiler control device that can improve responsiveness when the boiler load changes, a boiler system including the same, a boiler control method, and a boiler control program. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram illustrating a boiler according to an embodiment. [Figure 2] 1 is a schematic diagram showing a steam, condensate, and feedwater system in a boiler (a once-through boiler) according to one embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a hardware configuration of a boiler control device. [Figure 4] FIG. 2 is a functional configuration diagram showing an example of functions of the boiler control device according to the present embodiment. [Figure 5] FIG. 2 is a block diagram illustrating an example of a calculation process related to feedback control executed by the boiler control device according to the present embodiment. [Figure 6] FIG. 2 is a block diagram illustrating an example of a calculation process related to feedback control executed by the boiler control device according to the present embodiment. [Figure 7] 10 is a graph showing the behavior of each state parameter of the boiler when the load of the boiler according to the present embodiment increases. [Figure 8] 10 is a graph showing the behavior of each state parameter of the boiler when the load of the boiler according to the present embodiment increases. [Figure 9] 10 is a graph showing the behavior of each state parameter of the boiler when the load of the boiler according to the present embodiment is reduced. [Figure 10] 10 is a graph showing the behavior of each state parameter of the boiler when the load of the boiler according to the present embodiment is reduced. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention 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.

[0015] FIG. 1 is a schematic diagram showing the configuration of a boiler according to this embodiment.

[0016] The boiler 10 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.

[0017] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is a hollow rectangular cylinder installed vertically. The furnace wall 101 that forms the inner wall surface of the furnace 11 is made up of multiple water wall tubes and fins that connect the water wall tubes together, and recovers the heat generated by the combustion of pulverized fuel by heat exchange with the water and steam circulating inside the water wall tube, while also suppressing a temperature rise in the furnace wall 101.

[0018] The combustion device 20 is installed in the lower region of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, may be collectively referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged at equal intervals along the circumferential direction of the furnace 11 (for example, four burners installed at each corner of the rectangular furnace 11), and are arranged in multiple rows along the vertical direction as one set. Note that, for convenience of illustration, FIG. 1 shows only two burners from one set, and each set is denoted by the reference numerals 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace, the number of burner rows, the number of burners in one row, the arrangement of the burners, and the like are not limited to this embodiment.

[0019] Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, sometimes collectively referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, sometimes collectively referred to as "pulverized fuel supply pipes 22"). Mill 31 is, for example, a vertical roller mill having a pulverizing table (not shown) supported therein so as to be rotatable, and a plurality of pulverizing rollers (not shown) supported above the pulverizing table so as to be rotatable in conjunction with the rotation of the pulverizing table. The solid fuel pulverized by the cooperation of the pulverizing rollers and the pulverizing table is transported to a classifier (not shown) provided in mill 31 by primary air (carrier gas, oxidizing gas) supplied to mill 31. The classifier separates the pulverized fuel into pulverized fuel having a particle size smaller than that suitable for combustion in the burner 21 and coarse pulverized fuel having a particle size larger than that. The pulverized fuel passes through the classifier and is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. The coarse pulverized fuel that does not pass through the classifier falls onto the grinding table inside the mill 31 under its own weight and is re-ground.

[0020] An air register 23 is provided outside the furnace 11 at the installation position of the burner 21, and one end of an air duct 24 is connected to the air register 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), and is supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

[0021] The combustion gas passage 12 is connected to the vertical upper part of the furnace 11. The combustion gas passage 12 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 11 and feedwater or steam flowing inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to those shown in FIG. 1.

[0022] A flue 13 is connected to the downstream side of the combustion gas passage 12, and discharges the combustion gas whose heat has been recovered by the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, and heat is exchanged between the air flowing through the air duct 24 and the combustion gas flowing through the flue 13, heating the primary air supplied to the mill 31 and the secondary air supplied to the burner 21, thereby recovering further heat from the combustion gas after heat exchange with water and steam.

[0023] Furthermore, a denitration device 43 may be provided in the flue 13 at a position upstream of the air preheater 42. The denitration device 43 supplies a reducing agent, such as ammonia or urea water, which has the effect of reducing nitrogen oxides, to the combustion gas flowing through the flue 13, 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 43, thereby removing and reducing the nitrogen oxides in the combustion gas. A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental equipment such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, and a desulfurization equipment 46 that removes sulfur oxides, as well as an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental equipment. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas that has been treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0024] In the boiler 10, when the multiple mills 31 are driven, pulverized and classified pulverized fuel is supplied to the burner 21 together with primary air via the pulverized fuel supply pipe 22. Secondary air heated by the air preheater 42 is supplied to the burner 21 from the air duct 24 via the wind box 23. The burner 21 blows a pulverized fuel mixture, which is a mixture of pulverized fuel and primary air, into the furnace 11, and also blows secondary air into the furnace 11. The pulverized fuel mixture blown into the furnace 11 ignites and reacts with the secondary air to form a flame. A flame is formed in the lower region of the furnace 11, and high-temperature combustion gas rises within the furnace 11 and flows into the combustion gas passage 12. In this embodiment, air is used as the oxidizing gas (primary air, secondary air). However, the oxidizing gas may have a higher or lower oxygen content than air. By adjusting the ratio of the oxygen content to the supplied fuel flow rate within an appropriate range, stable combustion in the furnace 11 is achieved.

[0025] Additionally, above the mounting position of the burners 21 in the furnace 11, a plurality of additional air ports (AA ports) 25 are provided for supplying additional air for combustion (AA) into the furnace 11. The additional air ports 25 are connected to the ends of additional air ducts (AA ducts) 26 branching off from the air duct 24, and a portion of the air supplied from the forced draft fan 32 can be supplied to the additional air ports 25 via the additional air ducts 26 as additional air for combustion.

[0026] In region A (corresponding to the installation range of the wind box 23 in the height direction) inside the furnace 11 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 air flow rate (total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical air flow rate relative to the fuel flow rate supplied to the burner 21. This creates a reducing atmosphere in regions A and B (regions between the top of the burner 21 and the bottom of the additional air port 25) inside the furnace 11, and nitrogen oxides (NOx) generated by combustion are reduced inside the furnace 11. Thereafter, in region C (region above the bottom of the additional air port 25), additional combustion air is supplied from the additional air port 25 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.

[0027] The combustion gas that has flowed into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and an economizer 104 arranged inside the combustion gas passage 12, and is then discharged into the flue 13, where nitrogen oxides are removed in a denitration device 43, and the gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into the gas duct 41, where ash and the like are removed in a dust collector 44, and sulfur oxides are removed in a desulfurization device 46, and the gas is then discharged to the outside of the system from a chimney 47. Note that the arrangement of the heat exchangers in the combustion gas passage 12 and the arrangement of the devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow do not necessarily have to be in the order described above.

[0028] Next, a detailed description will be given of the superheater 102, reheater 103, and economizer 104 provided as heat exchangers in the combustion gas passage 12. Fig. 2 is a schematic diagram showing steam, condensate, and feedwater systems in a boiler (once-through boiler) according to one embodiment. 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 12, and the arrangement order of the heat exchangers relative to the combustion gas flow is not limited to that shown in Figure 1.

[0029] As shown in Figure 2, the power plant 1 of this embodiment includes a heat exchanger provided in the boiler 10, a steam turbine 111 that is rotationally driven by steam generated in the boiler 10, and a generator 113 that is connected to the steam turbine 111 and generates electricity using the rotational force of the steam turbine 111.

[0030] The steam turbine 111 is composed of, for example, a high-pressure turbine 111A, an intermediate-pressure turbine 111B, and a low-pressure turbine 111C. Steam heated by a superheater 102 of the boiler 10 drives the high-pressure turbine 111A, is reheated by a reheater 103 of the boiler 10, 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 drives the low-pressure turbine 111C is condensed into condensate 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 feedwater 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 as a heat source via an extraction line (not shown), and the feedwater supplied to the economizer 104 is heated.

[0031] For example, the case where the boiler 10 is a once-through boiler will be described. The economizer 104 is connected to the water wall tubes that make up the furnace wall 101. As the feedwater heated in the economizer 104 passes through the water wall tubes that make up the furnace wall 101, it is heated by radiation from the flame in the furnace 11 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.

[0032] Furthermore, during startup or low-load operation of the once-through boiler, the feedwater supplied from the economizer 104 may not all evaporate as it passes through the water wall tubes that make up the furnace wall 101, resulting in an operating state (wet operating state) in which a water level remains in the steam separator 125. In this wet operating state, the drain water separated in the steam separator 125 and discharged to the steam separator drain tank 126 may be circulated and supplied from the economizer 104 to the water wall tubes that make up the furnace wall 101 by using the boiler circulation pump (BCP) 127 to merge with the feedwater line L1 via the circulation line L6.

[0033] As the combustion gas flows through the combustion gas passage 12, heat is recovered from the combustion gas in the superheater 102, reheater 103, and economizer 104. Meanwhile, feedwater supplied from the boiler feed pump (BFP) 123 is preheated in the economizer 104, and then heated to become steam as it passes through the water wall tubes that make up the furnace wall 101. The steam separated in the steam separator 125 is introduced into the first superheater 102A, second superheater 102B, and 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 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.

[0034] The superheater 102 and the reheater 103 may be provided with means for controlling the temperature of the steam superheated in each heat exchanger (hereinafter, the temperature of the superheated steam at the outlet of the third superheater 102C is referred to as the "main steam temperature," and the temperature of the superheated steam at the outlet of the second reheater 103B is referred to as the "reheated steam temperature"). For example, a superheater spray valve (not shown) or a reheater spray valve (not shown) may be provided to control the steam temperature by adjusting the amount of water mixed and injected into the superheated steam (hereinafter, the water injected to control the main steam temperature is referred to as the "superheater spray water," and the water injected to control the reheated steam temperature is referred to as the "reheater spray water"). The superheater spray water and the reheater spray water are supplied, for example, by branching a portion of the feedwater to the boiler 10 from the outlet of the boiler feedwater pump 123. The position where the superheater spray water is mixed and injected is not limited to the outlet of the third superheater 102C, and may be any position where the main steam temperature can be controlled, for example, it may be installed at any position between the outlet of the steam separator 125 and the inlet of the high-pressure turbine 111A. Similarly, the position where the reheater spray water is mixed and injected is not limited to the outlet of the second reheater 103B, and may be any position where the reheat steam temperature can be controlled, for example, it may be installed at any position between the outlet of the high-pressure turbine 111A and the inlet of the intermediate-pressure turbine 111B.

[0035] Furthermore, a soot blower (ash removal device) (not shown) may be arranged in the combustion gas passage 12 in the gaps between the water wall tubes that make up each heat exchanger, such as the superheater 102, reheater 103, and economizer 104, or in the gaps between each heat exchanger. The soot blower is arranged to extend in a direction approximately perpendicular to the wall surface of the combustion gas passage 12. The soot blower is an injection device that injects steam (gas) in a direction perpendicular to the axial direction, with the axial direction being perpendicular to the wall surface of the combustion gas passage 12, and is also capable of varying the injection direction. Steam injected from the soot blower toward heat exchangers such as the superheater 102, reheater 103, and economizer 104 removes combustion ash that has adhered to and accumulated on the surface of the water wall tubes that make up the heat exchangers, preventing a decrease in the heat exchange efficiency of the water wall tubes.

[0036] Next, the boiler control device 200 according to this embodiment will be described. Fig. 3 is a diagram showing an example of the hardware configuration of a boiler control device 200. As shown in Fig. 3, the boiler control device 200 is a computer, and includes, for example, a CPU (Central Processing Unit: processor) 201, a main memory 202, a secondary storage 203, a communication interface 204, etc. The boiler control device 200 may also include an input device 205 that accepts input from a user, a display 206, etc. These components are connected via, for example, a bus 208.

[0037] The main memory device 202 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 201 and writing data processed by the programs. The secondary storage device 203 is a non-transitory computer-readable storage medium. Examples of the secondary storage device 203 include a magnetic disk such as a hard disk drive (HDD), a magneto-optical disk, a CD-ROM, a DVD-ROM, and a semiconductor memory such as a solid state drive (SSD).

[0038] Figure 4 is a functional configuration diagram showing an example of the functions of the boiler control device 200 according to this embodiment. The boiler control device 200 performs feedback control using information acquired by various sensors in order to operate the boiler stably. Furthermore, as will be described later, the control device 200 performs holding control to maintain the boiler feedwater flow rate (hereinafter simply referred to as the "main feedwater flow rate") command value at a predetermined value when the deviation between the planned value and the current value of a state parameter of the fluid flowing through the water wall tube, which changes in response to a change in boiler load, is equal to or greater than a predetermined threshold value and a predetermined time has elapsed since the start of the load change. The boiler control device 200 includes an acquisition unit 210, a calculation unit 211, and a control unit 212, as illustrated in FIG.

[0039] A series of processes for realizing the various functions described below is stored in the secondary storage device 203 (see FIG. 3) in the form of a program (e.g., a boiler control program), for example, and the CPU 201 reads this program into the main storage device 202 and executes information processing and arithmetic processing to realize the various functions. Note that the program may be pre-installed in the secondary storage device 203, provided in a state stored in another computer-readable storage medium, 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.

[0040] The acquisition unit 210 acquires state parameters of the fluid flowing through the water wall tube, the flow rate of which changes in response to changes in the boiler load. The acquisition unit 210 is, for example, a variety of sensors that detect state parameters of the fluid flowing through the water wall tube. Note that state parameters are, for example, the temperature of the water flowing through the water wall tube at the water wall tube outlet, the pressure of the water flowing through the water wall tube at the water wall tube outlet, etc. Furthermore, the planned values ​​of the state parameters based on the planned performance of the boiler and the current values ​​of the state parameters acquired by the acquisition unit 210 may be stored sequentially in the secondary storage device 203. Note that the planned values ​​and current values ​​of the state parameters based on the planned performance of the boiler may be, for example, the enthalpy of the water flowing through the water wall tube at the water wall tube outlet, etc. The measurement point for acquiring the current values ​​of these state parameters at the water wall tube outlet is, for example, the inlet of the steam separator 125. Furthermore, the "planned value of the state parameter based on the planned performance" means the design value of the state parameter in each part of the boiler to obtain the specified performance of the boiler, but is not necessarily limited to the numerical value at the design stage, and may be, for example, a numerical value that has been changed from the initial design value in consideration of performance changes over time.

[0041] In addition, the acquisition unit 210 may acquire various information necessary for boiler control, such as information regarding the output of the generator 113, information regarding the pressure of steam flowing into the inlet of the steam turbine 111 (main steam pressure at the steam turbine inlet), information regarding the main feedwater flow rate, information regarding the boiler load (the ratio of the amount of steam generated to the rated steam amount of the boiler system), the generator output target command, information regarding the boiler load (current boiler load) and the planned boiler load, deviation in steam temperature, and sensor information necessary for calculating the amount of heat received (for example, measured values ​​such as feedwater pressure, flow rate, temperature difference, etc.).

[0042] The calculation unit 211 calculates the deviation between the planned value of the state parameter based on the planned performance of the boiler and the current value of the state parameter acquired by the acquisition unit 210. The calculation unit 211 has the functions of, for example, a first-order lag element generator, a function generator, a comparator, an integrator, an adder, a PI (Proportional-Integral) controller, and a switch, and outputs a control command value for bringing the deviation between the planned value of the output in feedback control and the current value acquired by the acquisition unit 210 closer to zero.

[0043] The control unit 212 executes feedback control of the main feedwater flow rate in accordance with the deviation calculated by the calculation unit 211, and when the deviation is equal to or greater than a predetermined threshold, executes holding control, instead of feedback control, to hold the command value of the main feedwater flow rate at a predetermined value. Furthermore, the control unit 212 determines whether to execute feedback control or holding control, based on the deviation between the planned value and the current value calculated by the calculation unit 211.

[0044] For example, when the deviation between the planned value and the current value is equal to or greater than a predetermined threshold during a load change, and a predetermined time has elapsed since the start of the load change, the control unit 212 executes the holding control. In addition, the control unit 212 may output a command to switch the wiring in order to switch between the feedback control and the holding control.

[0045] The control device 200 may generate time information at a predetermined timing. The time information may be information about the time elapsed since the predetermined timing. The control unit 212 may determine, based on the time information, whether a predetermined time has elapsed since the start of the load change.

[0046] (Feedback control for boiler control) 5 and 6 are block diagrams illustrating the calculation steps related to feedback control executed by the boiler control device 200 according to this embodiment. Hereinafter, feedback control executed by the boiler control device according to this embodiment will be described with reference to FIGS. 5 and 6. Feedback control related to the governor opening, feedback control related to mill demand, and feedback control and holding control related to the main feedwater flow rate will be described. Note that in this embodiment, the calculations described below are performed by the calculation unit 211, but are not limited to this and may be performed by other components of the control device 200.

[0047] (Feedback control of governor opening) First, a description will be given of feedback control relating to a governor opening that adjusts the amount of steam supplied to the steam turbine 111. In the feedback control relating to the governor opening, for example, a load request command value for the steam turbine 111 is used. In the feedback control related to the governor opening, first, the acquisition unit 210 acquires a load request command value of the control system. Then, the acquisition unit 210 acquires information related to the governor opening. The information related to the governor opening includes, for example, the generator output, the ratio of the generator output to the rated output, and the rotational frequency of the steam turbine 111 connected to the generator.

[0048] The load request command value is a value calculated based on boiler operation information acquired by the acquisition unit 210. The load request command value is, for example, a target command for the generator output, information on the boiler load (current boiler load) and the target boiler load, deviation of the steam temperature, and sensor information required for calculating the amount of received heat (for example, measured values ​​of the pressure, flow rate, temperature difference, etc. of the feedwater). The load request command value may be determined appropriately using a known calculation method, and a detailed description thereof will be omitted.

[0049] The calculation unit 211 provides a first-order lag element via the first-order lag element generator LAG1 to the load request command value for the steam turbine 111 acquired by the acquisition unit 210. Then, the first-order lag element generator LAG1 outputs the load request command value for the steam turbine 111 to which the first-order lag element has been assigned to the comparator com1. Note that adding a first-order lag element to the command value of the rotational frequency of the steam turbine 111 is a process for stabilizing control in feedback control. The first-order lag element may be set appropriately for each process value based on empirical rules, simulations, test run results, etc.

[0050] The comparator com1 receives the load request command value acquired by the acquisition unit 210 and the output of the first-order lag element generator LAG1. The comparator com1 outputs the deviation between the load request command value and the rotational frequency of the steam turbine 111 to the PI controller PI1.

[0051] The PI controller PI1 performs proportional-integral control (PI control) based on the output value of the comparator com1. The PI controller PI1 outputs to the control unit 212 an operation amount for executing governor control of the steam turbine corresponding to the load request command value. Then, the control unit 212 executes governor control of the steam turbine based on the manipulated variable output from the PI controller PI1.

[0052] (Feedback control for mill demand) The following describes feedback control related to the fuel flow rate (hereinafter referred to as "mill demand") supplied to the mill 31. In the feedback control related to the mill demand, the acquisition unit 210 acquires, for example, a command value for the main steam temperature at the boiler outlet as information related to the mill demand. Furthermore, the acquisition unit 210 acquires a load request command value of the control system. Furthermore, the load request command value acquired by the acquisition unit 210 is input to a function generator F1. A function that outputs a planned value of the main steam temperature at the boiler outlet based on the input load request command value is set in the function generator F1. Then, the function generator F1 outputs the planned value of the main steam temperature at the boiler outlet to a comparator com2.

[0053] The comparator com2 outputs to the integrator I1 the deviation between the main steam temperature at the boiler outlet acquired by the acquisition unit 210 and the planned value of the main steam temperature at the boiler outlet output from the function generator F1. The integrator I1 integrates the deviation input from the comparator com2 and outputs the output value from which the steady-state deviation has been removed to the adder A1.

[0054] The adder A1 adds a base signal α based on the inlet main steam pressure of the steam turbine 111 to the output of the integrator I1, and outputs the resulting output value to the function generator F3.

[0055] Here, an example of the process by which the base signal α is calculated will be described. The first-order lag element generator LAG2 imparts a first-order lag element to a command value for the inlet main steam pressure of the steam turbine 111, corresponding to the inlet main steam pressure of the steam turbine 111 acquired by the acquisition unit 210. The first-order lag element generator LAG2 then outputs the command value for the inlet main steam pressure of the steam turbine 111 to which the first-order lag element has been applied to the comparator com3. The comparator com3 also receives an input of a planned value for the inlet main steam pressure of the steam turbine 111 based on a load request command value via a function generator F2. The comparator com3 outputs the deviation between the command value input from the first-order lag element generator LAG2 and the planned value input from the function generator F2 to the integrator I2. The integrator I2 integrates the deviation input from the comparator com3 and outputs an output value from which the steady-state deviation has been removed to the adder A2. The adder A2 adds the load request command value acquired by the acquisition unit 210 and the output value of the integrator I2, and outputs a base signal α.

[0056] A function generator F3 is set to output a command value for the fuel flow rate to be supplied to the boiler based on the output value of the adder A1, and outputs the command value for the fuel flow rate to be supplied to the boiler to the comparator com4. In addition, a command value for the fuel flow rate to be supplied to the boiler, to which a first-order lag element has been assigned by a first-order lag element generator LAG3 in response to the current value of the fuel flow rate to be supplied to the boiler acquired by the acquisition unit 210, is input to a comparator com4.

[0057] A comparator com4 calculates the deviation between the output value of the function generator F3 and the output value of the first-order lag element generator LAG3, and outputs the deviation to the PI controller PI2.

[0058] The PI controller PI2 performs proportional-integral control (PI control) based on the output value of the comparator com4. The PI controller PI2 outputs to the control unit 212 an operation amount for executing control of the fuel flow rate corresponding to the load request command value, in accordance with the load request command value, the main steam temperature at the boiler outlet, and the current values ​​of the fuel flow rate. The control unit 212 then controls the flow rate of fuel supplied to the mill based on the manipulated variable output from the PI controller PI2.

[0059] (Feedback control of main water supply flow rate) The feedback control performed by the boiler control device according to this embodiment also includes feedback control of the main feedwater flow rate. As shown in Fig. 6, the feedback control of the main feedwater flow rate performs the processes of process flow1 and process flow2 in parallel using a base signal α, and controls the main feedwater flow rate based on the processing results of each process.

[0060] Process flow 1 is a process for outputting a manipulated variable related to the main feedwater flow rate calculated based on the deviation between the set value and the current value of the main feedwater flow rate. Process flow 2 is a process for outputting a manipulated variable related to the main feedwater flow rate calculated based on the load request command value, etc.

[0061] Process flow 1 will be explained below. The function generator F4a is set with a function that outputs a manipulated variable related to the main feedwater flow rate, for example, a command value for the opening of the main feedwater flow rate adjustment valve, based on the input base signal α. The function generator F4a then outputs the command value for the opening of the main feedwater flow rate adjustment valve to the switch SW1.

[0062] Based on a hold control execution command output from the control unit 212, the switch SW1 switches between a connection for performing feedback control and a connection for performing hold control. For example, if the deviation between the planned and current temperature values ​​of the water flowing through the water wall tube at the water wall tube outlet during a load change is equal to or greater than a predetermined threshold value and a predetermined time has elapsed since the load change began, the control unit 212 switches the wiring of switch SW1 and executes holding control. Also, if the deviation between the planned and current temperature values ​​of the water flowing through the water wall tube at the water wall tube outlet during a load change is equal to or greater than a predetermined threshold value and a predetermined time has not elapsed since the load change began, the control unit 212 does not execute holding control and executes feedback control.

[0063] When the control unit 212 performs feedback control, the output value of the switch SW1 is output to the change rate limiter LIM1 via path r1. When the control unit 212 performs holding control, the output value of the switch SW1 is output to the switch SW1 via path r2. When holding control is being performed, the command value for the opening of the main feedwater flow rate adjustment valve is held at a predetermined value without changing.

[0064] The change rate limiter LIM1 limits the amount of change in the command value for the opening of the main feedwater flow rate adjustment valve when the command value for the opening of the main feedwater flow rate adjustment valve input from the switch SW1 changes suddenly. The change rate limiter LIM1 smoothes the command value for the opening of the main feedwater flow rate adjustment valve. For example, when the command value for the opening of the main feedwater flow rate adjustment valve changes in a step-like manner, it converts it into a slope-like manner. The change rate limiter LIM1 outputs the smoothed main feedwater flow rate to the comparator com5.

[0065] In addition, the comparator com5 receives as input the command value for the opening of the main water supply flow control valve to which a first-order delay element has been assigned by the first-order delay element generator LAG4 in relation to the current value of the command value for the opening of the main water supply flow control valve acquired by the acquisition unit 210.

[0066] A comparator com5 calculates the deviation between the output value of the change rate limiter LIM1 and the output value of the first-order lag element generator LAG4, and outputs the deviation to a PI controller PI3.

[0067] The PI controller PI3 performs proportional-integral control (PI control) based on the output value of the comparator com5, and outputs a command value for the opening of the main feedwater flow rate adjustment valve to the adder A3.

[0068] Next, a process flow 2 that is performed in parallel with the process flow 1 will be described. The function generator F4b is set with a function that outputs a manipulated variable related to the main feedwater flow rate, for example, a command value for the opening of the main feedwater flow rate adjustment valve, based on the input base signal α. Then, the function generator F4b outputs the command value for the opening of the main feedwater flow rate adjustment valve to the switch SW2.

[0069] Similar to the switch SW1, the switch SW2 switches between a connection for performing feedback control and a connection for performing holding control based on a holding control execution command output from the control unit 212. For example, if the deviation between the planned and current temperature values ​​of the water flowing through the water wall tube at the water wall tube outlet during a load change is equal to or greater than a predetermined threshold value and a predetermined time has elapsed since the load change began, the control unit 212 switches the wiring of switch SW2 and executes holding control. Also, if the deviation between the planned and current temperature values ​​of the water flowing through the water wall tube at the water wall tube outlet during a load change is equal to or greater than a predetermined threshold value and a predetermined time has not elapsed since the load change began, the control unit 212 does not execute holding control and executes feedback control. Moreover, the wiring of the switch SW2 is switched in synchronization with the wiring of the switch SW1 so as to correspond to the wiring of the switch SW1.

[0070] When the control unit 212 performs feedback control, the output value of the switch SW2 is output to the change rate limiter LIM2 via path r3. When the control unit 212 performs holding control, the output value of the switch SW2 is output to the switch SW2 via path r4. When holding control is being performed, the command value for the opening of the main feedwater flow rate adjustment valve does not change and is held at a predetermined value.

[0071] The change rate limiter LIM2 limits the amount of change in the command value for the opening of the main feedwater flow rate adjustment valve when the command value for the opening of the main feedwater flow rate adjustment valve input from the switch SW2 changes suddenly. The change rate limiter LIM2 smoothes the command value for the opening of the main feedwater flow rate adjustment valve. For example, when the command value for the opening of the main feedwater flow rate adjustment valve changes in a step-like manner, the change rate limiter LIM2 converts the opening of the main feedwater flow rate adjustment valve into a slope-like form. The change rate limiter LIM2 outputs the smoothed opening of the main feedwater flow rate adjustment valve to the adder A3.

[0072] The adder A3 adds the command value for the opening of the main feedwater flow control valve input from the PI controller PI3, which is the output value of process flow1, to the command value for the opening of the main feedwater flow control valve input from the rate of change limiter LIM2, which is the output value of process flow2, and outputs the command value for the opening of the feedwater flow control valve to the control unit 212. Then, the control unit 212 controls the main water feed flow rate based on the command value for the opening degree of the water feed flow rate adjustment valve input from the adder A3.

[0073] As described above, when the load changes, the control unit 212 switches the connections of switch SW1 and switch SW2 depending on the deviation between the planned value and the current value of the temperature of the water flowing through the water wall tube at the water wall tube outlet, and whether or not a predetermined time has passed since the load change began.

[0074] (For each boiler status parameter) Figures 7 to 10 are graphs showing the behavior of each boiler state parameter when feedback control and maintenance control are performed. Figures 7 and 8 are graphs showing the behavior of each boiler state parameter when the boiler load increases. Figures 9 and 10 are graphs showing the behavior of each boiler state parameter when the boiler load decreases. 7 to 10, the start time of the load change on the boiler is set to time t1, and the end time of the load change on the boiler is set to time t2.

[0075] Using Figures 7 and 8, the behavior of each boiler state parameter when the boiler load increases will be compared. In Fig. 7, the solid line shows the change in mega watt demand (MWD), which corresponds to the required command value for the boiler load. The dashed-dotted line shows the planned value of the fluid temperature at the water wall tube outlet. The two-dot chain line shows the change in the current value of the fluid temperature of the water flowing through the water wall tube at the water wall tube outlet when the control device 200 of this embodiment controls the boiler. The broken line shows the main feedwater flow rate. The thick two-dot chain line is an example of the current value of the fluid temperature of the water flowing through the water wall tube at the water wall tube outlet when operating with feedback control only, without holding control. Furthermore, while the main feedwater flow rate is changing, the control unit 212 is performing feedback control, and while the main feedwater flow rate is constant, the control unit 212 is performing holding control.

[0076] In the section from time t1 to time t2 when the MWD rises, the boiler is controlled to increase the main feedwater flow rate and fuel supply rate in response to the rise in MWD. ​​If the boiler is controlled using feedback control alone, the main feedwater flow rate increases quickly, but the fuel flow rate increases with a delay. For this reason, if the boiler's state parameters are controlled using feedback control alone, the main feedwater flow rate will temporarily exceed the appropriate amount corresponding to the fuel flow rate. As a result, the fluid temperature at the water wall tube outlet temporarily drops (see the thick two-dot chain line in Figure 7).

[0077] Compare the normal two-dot chain line and the thick two-dot chain line in Figure 7. In Figure 7, the deviation between the dot chain line and the normal two-dot chain line is smaller than the deviation between the dot chain line and the thick two-dot chain line. Furthermore, the normal two-dot chain line has better responsiveness to the dot chain line than the thick two-dot chain line. In other words, the control unit 212 controls the boiler by appropriately switching between feedback control and holding control, thereby improving the responsiveness of the boiler control.

[0078] In Fig. 8, the solid line indicates the mega watt demand (MWD) corresponding to the boiler load. The dashed line indicates the superheater spray water flow rate. The thick dashed line is an example of the superheater spray water flow rate when operating with feedback control only, without holding control.

[0079] Compare the normal dashed line and the thick dashed line in Figure 8. The fluctuation range of the superheater spray water flow rate indicated by the normal dashed line is smaller than the fluctuation range of the superheater spray water flow rate indicated by the thick dashed line. In other words, the control unit 212 controls the boiler by appropriately switching between feedback control and maintenance control, thereby improving the responsiveness of the control of the superheater spray water flow rate.

[0080] Next, the behavior of each boiler state parameter when the boiler load is reduced will be compared using Figs. In Fig. 9, the solid line indicates mega watt demand (MWD), which corresponds to the required command value for the boiler load. The dashed-dotted line indicates the planned value of the fluid temperature at the water wall tube outlet. The two-dot chain line indicates the current value of the temperature of the water flowing through the water wall tube at the water wall tube outlet when the control device 200 of this embodiment controls the boiler. The broken line indicates the main feedwater flow rate. The thick two-dot chain line is an example of the current value of the fluid temperature of the water flowing through the water wall tube at the water wall tube outlet when operation is performed using feedback control only, without holding control. Furthermore, the control unit 212 performs feedback control while the main feedwater flow rate is changing, and performs holding control while the main feedwater flow rate is constant.

[0081] In the section from time t1 to time t2 when the MWD decreases, the boiler is controlled to reduce the main feedwater flow rate and fuel supply rate in response to the decrease in MWD. ​​If the boiler is controlled using feedback control alone at this time, the main feedwater flow rate will decrease quickly, but the fuel flow rate will decrease with a delay relative to the decrease in the main feedwater flow rate. For this reason, if the various state variables of the boiler are controlled using feedback control alone, the main feedwater flow rate will temporarily become less than the appropriate amount corresponding to the fuel flow rate, and the fluid temperature at the water wall tube outlet will temporarily rise (see the thick two-dot chain line in Figure 9).

[0082] Compare the normal two-dot chain line and the thick two-dot chain line in Figure 9. In Figure 9, the deviation between the dot chain line and the normal two-dot chain line is smaller than the deviation between the dot chain line and the thick two-dot chain line. Furthermore, the normal two-dot chain line has better responsiveness to the dot chain line than the thick two-dot chain line. In other words, the control unit 212 controls the boiler by appropriately switching between feedback control and holding control, thereby improving the responsiveness of the boiler control.

[0083] In Fig. 10, the solid line indicates the mega watt demand (MWD) corresponding to the boiler load. The dashed line indicates the superheater spray water flow rate. The thick dashed line is an example of the superheater spray water flow rate when operating with feedback control only, without holding control.

[0084] Compare the normal dashed line and the thick dashed line in Figure 10. The fluctuation range of the superheater spray water flow rate indicated by the normal dashed line is smaller than the fluctuation range of the superheater spray water flow rate indicated by the thick dashed line. In other words, the control unit 212 controls the boiler by appropriately switching between feedback control and maintenance control, thereby improving the responsiveness of the control of the superheater spray water flow rate.

[0085] As described above, the control device 200 controls the operation of the boiler by appropriately switching between feedback control and holding control, thereby improving the responsiveness of the boiler control compared to when the operation of the boiler is controlled by feedback control alone.

[0086] According to the control device 200 of the above-described embodiment, the control unit 212 executes feedback control of the boiler feedwater flow rate based on the planned and current values ​​of the state parameters of the fluid flowing through the water wall tube when the load on the boiler 10 changes. The control unit 212 executes holding control when the deviation between the planned and current values ​​of the state parameters of the fluid flowing through the water wall tube when the load on the boiler 10 changes is equal to or greater than a predetermined threshold, and a predetermined time has elapsed since the start of the load change. By having the control unit 212 execute holding control, it is possible to prevent a temporary drop in the temperature of the water flowing through the water wall tube at the water wall tube outlet, for example, when the load on the boiler 10 increases. Furthermore, it is possible to prevent a drop in the temperature of the fluid flowing into the superheater or reheater located downstream of the water wall tube. In this way, the control unit 212 controls the boiler by appropriately switching between feedback control and holding control, thereby improving the responsiveness of the boiler when the load on the boiler changes.

[0087] Although the present disclosure has been described above using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments without departing from the gist of the present disclosure, and such modifications or improvements are also included in the technical scope of the present disclosure. Furthermore, the above embodiments may be combined as appropriate.

[0088] In the above-described embodiment, the boiler 10 of the present disclosure has been described as a boiler that uses solid fuel as fuel. Examples of solid fuels that can be used in the boiler include coal, biomass fuel, petroleum coke (PC) fuel, and petroleum residue.

[0089] Furthermore, in the above embodiment, the temperature of the water flowing through the water wall tube at the water wall tube outlet was described as a state parameter, but this is not a limitation. The state parameters may also include the pressure at the water wall tube outlet, and the planned and current values ​​of the state parameter may be the enthalpy at the water wall tube outlet.

[0090] In this case, the control unit 212 of the control device 200 executes holding control when the deviation between the planned value and the current value of enthalpy at the water wall tube outlet is equal to or greater than a predetermined threshold and a predetermined time has elapsed since the start of the load change. If the enthalpy is calculated using the pressure and temperature at the water wall tube outlet, the state of the fluid flowing through the water wall tube can be detected reliably even if the temperature at the water wall tube outlet reaches the saturation temperature. This allows the control unit 212 to execute holding control with more accurate timing, and improves the responsiveness of the boiler when the load changes.

[0091] In addition to the configuration of the above-described embodiment, the control unit 212 included in the control device 200 may set the change rates of the fuel flow rate and the air flow rate to values ​​greater than the target load change rate of the boiler. In this case, even if the fuel flow rate and the air flow rate temporarily deviate from the planned values ​​corresponding to the load change of the boiler 10, the fuel flow rate and the air flow rate can be quickly brought closer to the planned values ​​corresponding to the load change of the boiler 10. This can improve the responsiveness of the boiler when the load changes.

[0092] (Additional notes) The boiler control device, the boiler system including the same, the boiler control method, and the boiler control program described in each of the above-described embodiments can be understood, for example, as follows. A boiler control device (200) according to a first aspect of the present disclosure comprises an acquisition unit (210) that acquires state parameters of a fluid flowing through a water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation unit (211) that calculates the deviation between a planned value of the state parameter based on the planned performance of the boiler and the current value of the state parameter acquired by the acquisition unit; and a control unit (212) that executes feedback control of the boiler feedwater flow rate in accordance with the deviation, and, when the deviation is equal to or greater than a predetermined threshold, executes holding control to hold the command value of the feedwater flow rate at a predetermined value instead of the feedback control.

[0093] According to the boiler control device disclosed herein, the control unit performs feedback control of the boiler feedwater flow rate based on the current and planned values ​​of a state parameter of the fluid flowing through the water wall tube when the boiler load changes, and performs holding control, instead of feedback control, to hold the feedwater flow rate command value at a predetermined value when the deviation between the current and planned values ​​of the state parameter is equal to or greater than a predetermined threshold. When the boiler load increases, the water wall tube outlet temperature of the water flowing through the boiler's water wall tube temporarily drops, which also reduces the temperature of the fluid flowing into the superheater and reheater located downstream of the water wall tube, potentially worsening the responsiveness of the steam temperature characteristics. To prevent this from worsening, the control unit holds the feedwater flow rate command value at a predetermined value when the deviation between the current and planned values ​​of the state parameter is equal to or greater than a predetermined threshold until the deviation falls below the predetermined threshold. This improves the responsiveness of the boiler when the load changes.

[0094] A boiler control device according to a second aspect of the present disclosure is the first aspect, wherein the state parameter is the temperature of the water flowing through the water wall tube at the water wall tube outlet.

[0095] According to the boiler control device of the present disclosure, the state parameter is the water wall tube outlet temperature of the water flowing through the water wall tube. In this way, by controlling the command value for the feedwater flow rate to the boiler based on the deviation in the water wall tube outlet temperature of the water flowing through the water wall tube, it is possible to prevent deterioration of the steam temperature characteristics during boiler operation.

[0096] A boiler control device according to a third aspect of the present disclosure is the first aspect, wherein the state parameters further include pressure at the water wall tube outlet, and the planned value and the current value are enthalpy at the water wall tube outlet.

[0097] In the boiler control device according to the present disclosure, the state parameters further include the pressure at the water wall tube outlet, and the planned and current values ​​of the state parameters are enthalpy at the water wall tube outlet. If the enthalpy is calculated using the pressure and temperature at the water wall tube outlet, it is possible to reliably detect the state of the fluid flowing through the water wall tube, even if the temperature at the water wall tube outlet reaches the saturation temperature. This allows the control unit to perform holding control with more accurate timing, and improves responsiveness when the boiler load changes.

[0098] A boiler control device according to a fourth aspect of the present disclosure is any one of the first to third aspects, wherein the control unit executes the holding control when a predetermined time has elapsed since the start of the load change.

[0099] According to the boiler control device of the present disclosure, a deviation occurs between the planned value and the current value of the state parameter before the predetermined time has elapsed, and therefore the control unit executes feedback control to eliminate the deviation. This allows the maintenance control to be executed at a more appropriate timing, thereby improving the responsiveness when the boiler load changes.

[0100] A boiler control device according to a fifth aspect of the present disclosure is any one of the first to fourth aspects, wherein the control unit sets the rate of change of the fuel flow rate and the air flow rate to a value greater than the target load rate of change of the boiler.

[0101] In the boiler control device according to the present disclosure, the control unit sets the rate of change of the fuel flow rate and the air flow rate to values ​​greater than the target rate of change of the boiler load. Therefore, even if the fuel flow rate and the air flow rate temporarily deviate from the planned value corresponding to the boiler load change, the fuel flow rate and the air flow rate can be quickly brought closer to the planned value corresponding to the boiler load change. This improves the responsiveness of the boiler to changes in load.

[0102] A boiler system according to a sixth aspect of the present disclosure includes a boiler control device according to any one of the first to fifth aspects, and a boiler (10) that burns pulverized fuel made from pulverized solid fuel using a burner and exchanges the heat generated by the combustion with feedwater or steam to generate superheated steam.

[0103] A boiler control method according to a seventh aspect of the present disclosure comprises an acquisition step of acquiring state parameters of a fluid flowing through a water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation step of calculating the deviation between a planned value of the state parameter based on the planned performance of the boiler and the current value of the state parameter acquired in the acquisition step; and a control step of executing feedback control on a command value for the boiler feedwater flow rate according to the deviation, and, if the deviation is equal to or greater than a predetermined threshold, executing holding control to hold the command value for the feedwater flow rate at a predetermined value instead of the feedback control.

[0104] A boiler control program according to an eighth aspect of the present disclosure causes a computer to function as the boiler control device according to any one of the first to fifth aspects. [Explanation of symbols]

[0105] 1. Power Plant 10. Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion equipment 21 Burner 22 Fine fuel supply pipe 23 Air register 24 Air duct 25 Additional air port 26 Additional air duct 31 Mill (Grinder) 32 Forced draft fan (FDF) 41 Gas duct 42 Air preheater 43 Denitration equipment 44 Dust collection device 45 Induced Draft Fan (IDF) 46 Desulfurization equipment 47 Chimney 101 Furnace wall 102 Superheater 102A 1st superheater 102B 2nd superheater 102C 3rd superheater 103 Reheater 103A 1st reheater 103B 2nd reheater 104 Economizer 111 Steam turbine 111A high pressure turbine 111B Intermediate Pressure Turbine 111C low pressure turbine 112 Condenser 113 Generator 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 127 Boiler Circulation Pump (BCP) 200 control device 201 CPU 202 Main storage 203 Secondary storage device 204 Communication Interface 205 Input Devices 206 Display 208 Bus 210 Acquisition Department 211 Arithmetic section 212 Control Unit A1~A3 adder com1~com4 comparator F1~F4b Function generator I1,I2 integrator L1 water supply line L2 drain water line L3~L5 steam lines L6 Circulation Line LAG1~LAG4 First-order lag element generator LIM1, LIM2 rate of change limiter PI1~PI3 PI controllers α base signal

Claims

1. an acquisition unit that acquires state parameters of the fluid flowing through the water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation unit that calculates a deviation between a planned value of the state parameter based on a planned performance of the boiler and a current value of the state parameter acquired by the acquisition unit; a control unit that executes feedback control regarding the boiler feedwater flow rate in accordance with the deviation, and, when the deviation is equal to or greater than a predetermined threshold, executes holding control to hold the command value of the feedwater flow rate at a predetermined value instead of the feedback control; A boiler control device comprising:

2. 2. A boiler control device according to claim 1, wherein the state parameter is the temperature of the water flowing through the water wall tube at the water wall tube outlet.

3. the state parameters further include a pressure at the water wall tube outlet; 3. A boiler control device according to claim 2, wherein the planned value and the current value are enthalpies at the outlet of the water wall tube.

4. The boiler control device according to claim 1 , wherein the control unit executes the holding control when a predetermined time has elapsed since the start of the load change.

5. The boiler control device according to claim 1 , wherein the control unit sets the change rates of the fuel flow rate and the air flow rate to values ​​greater than the target load change rate of the boiler.

6. The boiler control device according to any one of claims 1 to 5; A boiler that burns pulverized solid fuel with a burner and exchanges the heat generated by the combustion with feedwater or steam to generate superheated steam. A boiler system comprising:

7. an acquisition step of acquiring state parameters of the fluid flowing through the water wall tube, the flow rate of which changes in response to changes in the boiler load; a calculation step of calculating a deviation between a planned value of the state parameter based on a planned performance of the boiler and a current value of the state parameter acquired in the acquisition step; a control step of executing feedback control on a command value of a boiler feedwater flow rate in accordance with the deviation, and, when the deviation is equal to or greater than a predetermined threshold, executing a holding control for holding the command value of the feedwater flow rate at a predetermined value instead of the feedback control; A method for controlling a boiler having the above construction.

8. A boiler control program that causes a computer to function as the boiler control device according to any one of claims 1 to 5.

Images