Boiler control device, boiler, boiler control method and boiler control program

Abstract

To provide a boiler control device capable of estimating a fuel heating amount to stably operating a boiler, a boiler, a boiler control method, and a boiler control program.SOLUTION: A boiler control device 50 for controlling a boiler, comprises a state quantity acquisition unit 51 that acquires a state quantity of the boiler, and a calculation unit 52 that calculates a fuel calorific value, which is a heating value of fuel input to the boiler, based on the state quantity of the boiler and boiler efficiency that is preset in the boiler control device 50. When a fluctuation amount in the fuel calorific value calculated by the calculation unit 52 satisfies a predetermined condition, the fuel calorific value is used to perform control to correct a fuel flow rate input to the boiler.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] A large boiler such as a power generation boiler has a hollow furnace that is installed vertically, and a plurality of burners are arranged on the furnace wall along the circumferential direction of the furnace. In addition, a flue is connected to the large boiler vertically above the furnace, and a heat exchanger for generating steam is arranged in the flue. The burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame, and combustion gas is generated and flows into the flue. A heat exchanger is installed in the area where the combustion gas flows, and water or steam flowing inside a heat transfer tube that constitutes the heat exchanger is heated to generate superheated steam.

[0003] In order to stably operate and control a boiler, it is necessary to correctly grasp the amount of heat input to the boiler. The amount of heat input to the boiler can be obtained based on the fuel flow rate and the fuel heating value (calories). For example, Patent Document 1 discloses a method of calculating the amount of heat using the boiler efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-337112 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention of Patent Document 1, the measured value obtained from the boiler to calculate the calorific value fluctuates, so the calorific value fluctuates frequently, resulting in a problem of poor stabilization of the fuel flow rate control.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a boiler control device, a boiler, a boiler control method, and a boiler control program that estimate a fuel calorific value and operate a boiler stably. [Means for solving the problem]

[0007] In order to solve the above problems, the boiler control device, boiler, boiler control method, and boiler control program disclosed herein employ the following means. The boiler control device disclosed herein is a boiler control device that controls a boiler, and includes a state quantity acquisition unit that acquires state quantities of the boiler, and a calculation unit that calculates a fuel calorific value, which is the heat value of fuel input to the boiler, based on the state quantities of the boiler and a boiler efficiency that is preset in the boiler control device, and when a fluctuation amount of the fuel calorific value calculated by the calculation unit satisfies a predetermined condition, the boiler control device performs control to correct the flow rate of fuel input to the boiler using the fuel calorific value.

[0008] The boiler of the present disclosure includes the above-mentioned boiler control device, and is controlled by the boiler control device.

[0009] The boiler control method disclosed herein is a boiler control method for controlling a boiler, and includes a state quantity acquisition step of acquiring a state quantity of the boiler, and a calculation step of calculating a fuel calorific value, which is the heat value of fuel input to the boiler, based on the state quantity of the boiler and a preset boiler efficiency, and when a fluctuation amount of the fuel calorific value calculated by the calculation step satisfies a predetermined condition, a computer executes control to correct the flow rate of fuel input to the boiler using the fuel calorific value.

[0010] The boiler control program of the present disclosure causes a computer to execute the above-mentioned boiler control method. Effect of the Invention

[0011] According to the present disclosure, excessive correction of the boiler fuel flow rate control can be avoided, and the stabilization of the fuel flow rate control is improved. [Brief description of the drawings]

[0012] [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. [Diagram 2] FIG. 2 is a schematic diagram illustrating a heat exchanger in a boiler in accordance with some embodiments of the present disclosure. [Diagram 3] FIG. 2 is a diagram illustrating an example of a hardware configuration of a boiler control device in some embodiments of the present disclosure. [Figure 4] FIG. 2 is a diagram illustrating an example of the functionality of a boiler control device in some embodiments of the present disclosure. [Diagram 5] FIG. 11 is a diagram showing, as a reference example, calculation of a fuel flow rate command when the amount of heat generated fluctuates. [Figure 6] FIG. 11 is a diagram showing calculation of an estimated heat generation amount as a reference example. [Figure 7] FIG. 13 is a diagram illustrating a calculation of a fuel flow rate command by a boiler control device in some embodiments of the present disclosure when the heat generation amount fluctuates. [Figure 8] FIG. 2 illustrates a calculation of fuel heating value by a boiler control device in some embodiments of the present disclosure. [Figure 9] 11 is a diagram showing a time progression of a heat generation amount estimated moving average value and a heat generation amount correction in some embodiments of the present disclosure. [Figure 10] FIG. 2 is a control flowchart of a boiler control device in some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of a boiler control device, a boiler, a boiler control method, and a boiler control program according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to this embodiment, and when there are multiple embodiments, the present disclosure also includes a configuration in which each embodiment is combined. In the following description, up and above refer to the upper side in the vertical direction, and down and below refer to the lower side in the vertical direction, and the vertical direction is not precise and includes an error.

[0014] FIG. 1 is a schematic diagram showing a boiler using solid fuel as a main fuel in some embodiments of the present disclosure.

[0015] 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 feed water or steam. Biomass fuel, coal, etc. are used as the solid fuel.

[0016] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylinder shape and is installed vertically. The furnace wall 101 constituting the inner wall surface of the furnace 11 is composed of a plurality of heat transfer tubes and fins connecting the heat transfer tubes, and recovers heat generated by the combustion of pulverized fuel by heat exchange with water and steam flowing inside the heat transfer tubes, while suppressing the temperature rise of the furnace wall 101.

[0017] 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, they may be collectively referred to as "burners 21") attached to the furnace wall 101. The burners 21 are arranged in a plurality of stages along the vertical direction, with each set being 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). For convenience of illustration, only two burners 21 of one set are shown in FIG. 1, and each set is denoted by the reference numerals 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace 11, the number of stages of the burners 21, the number of burners 21 in one stage, the arrangement of the burners 21, and the like are not limited to this embodiment.

[0018] The 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"). The mill 31 is, for example, a vertical roller mill in which a pulverizing table (not shown) is supported inside so as to be rotatable and a plurality of pulverizing rollers (not shown) are 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 the mill 31 by primary air (transport gas, oxidizing gas) supplied to the mill 31. In the classifier, the fuel particles are classified into pulverized fuel having a particle size equal to or 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 by its own weight inside the mill 31 and is re-ground.

[0019] An air register 23 is provided on the outside of the furnace 11 at the mounting 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: Forced Draft Fan) 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 is introduced into the furnace 11.

[0020] 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 feed water or steam flowing inside each heat exchanger. The arrangement and shape of each heat exchanger are not limited to the form shown in FIG. 1.

[0021] 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, thereby 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.

[0022] 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 having an effect of reducing nitrogen oxides, such as ammonia or urea water, to the combustion gas flowing through the flue 13, and promotes a 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, for removing ash and the like from the combustion gas, a desulfurization equipment 46 for removing sulfur oxides, and an induced draft fan (IDF) 45 for directing 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 treated in the environmental equipment is discharged to the outside of the system as exhaust gas.

[0023] In the boiler 10, when the multiple mills 31 are driven, the pulverized and classified pulverized fuel is supplied to the burner 21 together with the primary air through the pulverized fuel supply pipe 22. In addition, secondary air heated by the air preheater 42 is supplied to the burner 21 through the wind duct 24 and the wind box 23. The burner 21 blows a pulverized fuel mixture, which is a mixture of the pulverized fuel and the 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 the high-temperature combustion gas rises inside 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), but the oxidizing gas may have a higher or lower oxygen ratio than air, and stable combustion in the furnace 11 is achieved by adjusting the ratio of the amount of oxygen to the amount of fuel supplied to an appropriate range.

[0024] The combustion gas flowing into the combustion gas passage 12 exchanges heat with water and steam in a superheater 102, a reheater 103, and a coal 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 combustion gas exchanges heat with primary air and secondary air in an air preheater 42, and is then discharged into a 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 combustion 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 devices from the flue 13 to the gas duct 41 with respect to the combustion gas flow does not necessarily have to be in the order described above.

[0025] Next, a detailed description will be given of the superheater 102, the reheater 103, and the economizer 104 provided in the combustion gas passage 12 as heat exchangers. Fig. 2 is a schematic diagram showing heat exchangers provided in a boiler in some embodiments of the present disclosure. Note that FIG. 1 does not accurately show the positions of the heat exchangers (superheaters 102A, 102B, 102C, reheaters 103A, 103B, 103C, and economizer 104) in the combustion gas passage 12, and the arrangement order of the heat exchangers with respect to the combustion gas flow is not limited to that shown in FIG. 1.

[0026] As shown in FIG. 2, the power plant 1 of this embodiment includes a heat exchanger provided in a 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 by the rotational force of the steam turbine 111.

[0027] The steam turbine 111, which is rotationally driven by the steam generated in the boiler 10, is composed of, for example, a high-pressure turbine 111A, an intermediate-pressure turbine 111B, and a low-pressure turbine 111C. The steam heated by the superheater 102 of the boiler 10 drives the high-pressure turbine 111A, and is then reheated by the reheater 103 of the boiler 10 to drive 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 by heat exchange with cooling water (e.g., seawater or river water) in the condenser 112 to become condensed water. 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 part 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 supplied to the economizer 104 is heated.

[0028] For example, a case where the boiler 10 is a once-through boiler will be described. The economizer 104 is connected to a heat transfer tube constituting the furnace wall 101. The feed water heated by the economizer 104 is heated by radiation from the flame in the furnace 11 while passing through the heat transfer tube constituting the furnace wall 101, and is led to the steam separator 125. The steam separated by the steam separator 125 is supplied to the superheater 102, and the drain water separated by 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.

[0029] Furthermore, during startup or low load operation of the once-through boiler, the feedwater supplied from the economizer 104 may not be fully evaporated as it passes through the heat transfer tubes constituting the furnace wall 101, resulting in an operating state (wet operating state) in which the water level exists 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 heat transfer tubes constituting the furnace wall 101 by merging it midway through the feedwater line L1 using the boiler circulation pump (BCP) 127 via the circulation line L6.

[0030] When the combustion gas flows through the combustion gas passage 12, the heat of the combustion gas is recovered by the superheater 102, the reheater 103, and the economizer 104. On the other hand, the feed water supplied from the boiler feed pump (BFP) 123 is preheated by the economizer 104, and then heated to become steam when passing through the heat transfer tubes constituting the furnace wall 101, and is guided to the steam separator 125. The steam separated by the steam separator 125 is introduced into the first superheater 102A, the second superheater 102B, and the third superheater 102C, and is superheated by the combustion gas. The superheated steam generated by the superheater 102 is supplied to the high-pressure turbine 111A via the steam line L3, and drives the high-pressure turbine 111A to rotate. The steam discharged from the high-pressure turbine 111A is introduced into the first reheater 103A and the second reheater 103B via the steam line L4, and is superheated again. The re-superheated steam is supplied to the low-pressure turbine 111C via the steam line L5 and the intermediate-pressure turbine 111B, and rotates and drives the intermediate-pressure turbine 111B and the low-pressure turbine 111C. The rotating shaft of the steam turbine 111 rotates and drives the generator 113 to generate 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.

[0031] The superheater 102 and the reheater 103 may be provided with a 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 for controlling the steam temperature by adjusting the amount of water mixed and injected into the superheated steam (hereinafter, the water injected for controlling the main steam temperature is referred to as the "superheater spray water", and the water injected for controlling 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 part of the water supplied to the boiler 10 from the outlet of the boiler feed water 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 is 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 is installed at any position between the outlet of the high-pressure turbine 111A and the inlet of the intermediate-pressure turbine 111B.

[0032] In addition, in the combustion gas passage 12, a soot blower (ash removal device) (not shown) may be arranged in the gaps between the heat transfer tubes constituting each heat exchanger such as the superheater 102, the reheater 103, the economizer 104, or in the gaps between each heat exchanger. The soot blower is arranged extending 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 can also change the injection direction. The steam injected from the soot blower toward the heat exchangers such as the superheater 102, the reheater 103, the economizer 104 removes combustion ash that has adhered to and accumulated on the surfaces of the heat transfer tubes constituting the heat exchangers, and suppresses a decrease in the heat exchange efficiency of the heat transfer tubes.

[0033] In the above, the boiler 10 of the present disclosure has been described as a boiler that uses solid fuel as fuel. The solid fuel used in the boiler 10 may be coal, biomass fuel, petroleum coke (PC), petroleum residue, waste tires, or the like. The fuel for the boiler 10 is not limited to solid fuel, and may also be petroleum such as heavy oil, light oil, and heavy oil, industrial waste liquid, liquefied ammonia, and other liquid fuels. In addition, gaseous fuels such as natural gas, various petroleum gases, by-product gases generated in the steelmaking process, hydrogen gas, and ammonia gas may also be used. Furthermore, the boiler may be a multi-fuel boiler that uses a combination of these various fuels. For example, a combination of coal and biomass fuel (wood chips, pellets, etc.), a combination of a plurality of different types of biomass fuel, etc. may be used.

[0034] The boiler 10 of the present disclosure is controlled by a boiler control device 50.

[0035] FIG. 3 is a diagram illustrating an example of a hardware configuration of a boiler control device according to some embodiments of the present disclosure. 3, the boiler control device (Controller) 50 is a computer system, and includes, for example, a CPU (Central Processing Unit: Processor) 1100, a secondary storage device (ROM, Secondary storage: Memory) 1200, a main storage device (RAM, Main Memory) 1300, a hard disk drive (HDD) 1400 as a large-capacity storage device, and a communication unit 1500 for connecting to a network or the like. Note that a solid-state drive (SSD) may be used as the large-capacity storage device. These units are connected via a bus 1800.

[0036] The CPU 1100 controls the entire boiler control device 50 by, for example, an OS (Operating System) stored in a secondary storage device 1200 connected via a bus 1800, and executes various processes by executing various programs stored in the secondary storage device 1200. One or more CPUs 1100 may be provided, and may cooperate with each other to realize processes.

[0037] The main memory device 1300 is composed of writable memory such as cache memory or 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.

[0038] The secondary storage device 1200 is a non-transitory computer readable storage medium. The secondary storage device 1200 is, for example, a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Examples of the secondary storage device 1200 include a ROM (Read Only Memory), a HDD (Hard Disk Drive), and a SSD (Solid State Drive) flash memory. The secondary storage device 1200 stores, for example, an OS for controlling the entire information processing device such as Windows (registered trademark), iOS (registered trademark), Android (registered trademark), a BIOS (Basic Input / Output System), various device drivers for operating peripheral devices as hardware, various application software, and various data and files. In addition, the secondary storage device 1200 stores programs for implementing various processes and various data required for implementing various processes. A plurality of secondary storage devices 1200 may be provided, and the above-mentioned programs and data may be divided and stored in each secondary storage device 1200.

[0039] The boiler control device 50 may also include an input unit consisting of a keyboard, a mouse, etc., and a display unit consisting of a liquid crystal display device or the like for displaying data. The boiler control device 50 may also include a notification unit including a display unit, such as a lamp, a speaker for outputting sound, particularly an alarm sound, etc.

[0040] FIG. 4 is a diagram illustrating an example of the function of a boiler control device in some embodiments of the present disclosure. As shown in FIG. 4, the boiler control device 50 includes a state quantity acquisition unit 51 and a calculation unit 52.

[0041] A series of processes for realizing the functions of the boiler control device 50 is stored in the secondary storage device 1200 (see FIG. 3) in the form of a program, for example, and the CPU (processor) 1100 (see FIG. 3) reads this program into the main storage device 1300 (see FIG. 3) and executes information processing and arithmetic processing to realize various functions. Note that the program may be pre-installed in the secondary storage device 1200, 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.

[0042] The state quantity acquisition unit 51 shown in FIG. 4 acquires the state quantity of the boiler 10. The state quantities of the boiler 10 include the heat quantity Q1 of the steam discharged from the boiler 10, the heat quantity Q0 of the steam and feedwater flowing into the boiler 10, and the fuel flow rate Wf. The heat quantity Q1 of the steam discharged from the boiler 10 is calculated by multiplying the flow rate of the steam discharged from the boiler 10 by the enthalpy of the steam. The heat quantity Q0 of the steam and feedwater flowing into the boiler 10 is calculated by adding the heat quantity of the steam obtained by multiplying the flow rate of the steam flowing into the boiler 10 by the enthalpy of the steam, and the heat quantity of the feedwater obtained by multiplying the flow rate of the feedwater flowing into the boiler 10 by the enthalpy of the feedwater. The state quantity acquisition unit 51 calculates and acquires the heat quantity Q1 of the steam discharged from the boiler 10 and the heat quantity Q0 of the steam and feedwater flowing into the boiler 10 based on the measured steam flow rate and feedwater flow rate.

[0043] The calculation unit 52 calculates a fuel calorific value Hh, which is the calorific value of the fuel input to the boiler 10, based on each state quantity acquired by the state quantity acquisition unit 51 and a boiler efficiency η B preset in the boiler control device 50.

[0044] The boiler efficiency ηB is a value that fluctuates little, so in this embodiment it is a constant value. The boiler efficiency ηB may be a value according to the load of the boiler 10. The boiler efficiency ηB is set in advance in the boiler control device 50. The boiler efficiency ηB (%) is calculated by the following formula (1).

[0045]

number

[0046] In equation (1), Q1 is the calorific value of the steam leaving the boiler 10, Q0 is the calorific value of the steam and feed water flowing into the boiler 10, Wf is the actual fuel flow rate, and Hh is the fuel calorific value. Therefore, the fuel calorific value Hh can be calculated by the following equation (2).

[0047]

number

[0048] On the other hand, when multiple fuels with different fuel heating values ​​are input and mixed combustion is performed, the fuel flow rate and fuel heating value are expressed by the following equation (3).

[0049] [Number 3] W A ×H A +W B ×H B =W A+B ×H ave (3)

[0050] In equation (3), W A is the fuel flow rate of fuel A, H A is the fuel calorific value of fuel A, W B is the fuel flow rate of fuel B, H B is the fuel calorific value of fuel B, W A+B is the total fuel flow rate, i.e., W A +W B , H ave indicates the average heat value of fuel A and fuel B. In this case, the boiler efficiency ηB is calculated by the following equation (4).

[0051]

number

[0052] Substituting equation (3) into equation (4), we obtain the following equation (5).

[0053]

number

[0054] Therefore, from equation (5), the average heat value of multiple fuels, H ave can be calculated using the following equation (6).

[0055]

number

[0056] First, a reference example of boiler control when the calorific value fluctuates will be described. FIG. 5 is a diagram showing, as a reference example, calculation of a fuel flow rate command when the amount of heat generated fluctuates.

[0057] 5, MWD (Mega Watt Demand, required generator output) 60 is input to the boiler control device 50. In addition, the main steam pressure deviation (value obtained by subtracting the main steam pressure measurement value from the main steam pressure set value) 61 of the boiler 10 is input, proportionally integrated by a regulator (PI controller) 62, and added to the MWD 60 by an adder 63. The output value of the adder 63 becomes the input demand (MW) for the boiler 10.

[0058] The input demand of the boiler 10 is input to a function unit 64. The function unit 64 outputs a fuel flow rate setting (t / h) based on a preset relationship between the input demand of the boiler 10 and the fuel flow rate. This relationship between the input demand of the boiler 10 and the fuel flow rate is calculated using a design value (reference calorific value) of the fuel calorific value.

[0059] In an adder 66 , the fuel flow rate setting is added to a fuel flow rate correction 65 , which will be described later, and a fuel flow rate demand 67 is output.

[0060] A subtractor 71 subtracts a value (calorific value corrected fuel flow rate) obtained by correcting an actually measured fuel flow rate (measured value) 68 using an estimated calorific value 73 from a fuel flow rate demand 67, and outputs a fuel flow rate command 72. The calorific value corrected fuel flow rate is calculated as follows.

[0061] When an operator manually corrects the estimated heat generation amount 73 based on the process value of the boiler 10, a switch 74 is turned ON and the heat generation amount is estimated using a heat generation amount setting device 75. The automatic correction of the estimated heat generation amount 73 will be described later.

[0062] The estimated heat generation amount after manual correction (output of switch 74) is input to a divider 76, which uses the estimated heat generation amount after manual correction as the numerator and the reference heat generation amount 77 as the denominator, and outputs a heat generation amount correction coefficient (the ratio of the estimated heat generation amount after correction to the reference heat generation amount).

[0063] A multiplier 69 multiplies the fuel flow rate (measured value) 68 by the heat generation amount correction coefficient, and outputs the result as a heat generation amount corrected fuel flow rate.

[0064] FIG. 6 is a diagram showing the fuel flow rate correction and the automatic correction of the estimated heat generation amount using the main steam temperature deviation as a reference example. The fuel flow rate correction 65 and the automatic correction of the estimated heat generation amount 73 in FIG. 5 are performed as follows.

[0065] 6, a steam temperature setting 81, which is a control target value for the steam temperature, and an actually measured steam temperature (measured value) 82 are input to the boiler control device 50. A subtractor 83 subtracts the steam temperature (measured value) 82 from the steam temperature setting 81, and outputs the deviation of the steam temperature. The deviation of the steam temperature is proportionally integrated in a regulator (PI controller) 84.

[0066] The output value of the regulator 84 is set as the fuel flow rate correction 65, and transitions to FIG. In the output value of regulator 84, when steam temperature (measured value) 82 is below steam temperature setting 81, the steam temperature deviation becomes a positive value and a correction is made to increase fuel. Conversely, when steam temperature (measured value) 82 is equal to or higher than steam temperature setting 81, the steam temperature deviation becomes a negative value and a correction is made to decrease fuel.

[0067] On the other hand, the estimated heat generation amount 73 is automatically corrected by using a heat generation amount adjustment circuit 70. In the calorific value adjustment circuit 70, when the deviation of the steam temperature (set value and measured value) is small and no adjustment is required to increase or decrease the estimated calorific value, the input value to the regulator (PI controller) 90 is input as input value 87, which is 0%, and the estimated calorific value is not adjusted to increase or decrease and remains a constant value.

[0068] Furthermore, when the fuel flow rate correction value, which is the output value of regulator 84, becomes larger than a certain threshold value (positive value) set in upper limit monitor 85, a trigger is output from upper limit monitor 85 and switch 88 is turned ON. When the fuel flow rate correction value, which is the output value of regulator 84, becomes smaller than a certain threshold value (negative value) set in lower limit monitor 86, a trigger is output from lower limit monitor 86 and switch 89 is turned ON. Either switch 88 or 89 is turned ON.

[0069] When the switch 88 is turned ON, the steam temperature is lower than the set value, and the fuel flow rate must be increased. A negative value 92 is input to the regulator (PI controller) 90 to reduce the estimated heat generation amount 73, thereby increasing the fuel flow rate.

[0070] When switch 89 is turned ON, the steam temperature is higher than the set value, and the fuel flow rate must be reduced. A positive value 93 is input to regulator (PI controller) 90 to increase and correct the estimated heat generation amount 73, thereby reducing the fuel flow rate.

[0071] The output values ​​of the switches 88 and 89 are proportionally integrated by a regulator (PI controller) 90, and the output value of the regulator 90 is set as the estimated heat generation amount 73, causing a transition to FIG.

[0072] The estimated calorific value 73 is automatically corrected by the calorific value adjustment circuit 70 based on the steam temperature deviation, but since the fuel flow rate correction and the automatic calorific value correction cause control interference, it is necessary to perform the correction slowly to prevent this. Therefore, since the correction takes time, there is an issue that it cannot follow the actual fluctuation in the calorific value of the fuel.

[0073] Furthermore, if the operation of the boiler 10 is continued in a state where the calorific value of the fuel actually input to the boiler 10 is significantly outside the range of the calorific value of the fuel assumed by the boiler control device 50, the balance of the fuel, water, and air input to the boiler 10 will be lost from the ideal state, and restrictions may be imposed on the operation of the boiler 10. In particular, it may become impossible to perform a load change operation in the boiler 10. Ultimately, it may become impossible to continue the operation of the boiler 10, leading to a situation in which the boiler 10 is stopped.

[0074] Next, boiler control in some embodiments of the present disclosure will be described. 7 is a diagram showing calculation of a fuel flow command when the heat generation amount fluctuates by a boiler control device in some embodiments of the present disclosure. This embodiment is characterized by the calculation of the fuel heat generation amount compared to the reference example, and is otherwise similar to the reference example. Therefore, the following mainly describes the differences from the reference example.

[0075] As shown in FIG. 7, a multiplier 69 multiplies a fuel flow rate (measured value) 68 by a calorific value correction coefficient, and outputs the result as a calorific value-corrected fuel flow rate.

[0076] Here, the calorific value correction coefficient input to the multiplier 69 is the output value of a divider 76 when the numerator is the fuel calorific value 80 and the denominator is the reference calorific value 77, which is the design value of the fuel calorific value.

[0077] The fuel calorific value 80 input to the divider 76 is the fuel calorific value 80 calculated based on the boiler efficiency η B calculated from equation (2).

[0078] In a divider 76, the numerator is the fuel calorific value 80 calculated based on the boiler efficiency ηB, and the denominator is the reference calorific value 77, which is the fuel calorific value of the design value, and the result is output as a calorific value correction coefficient. In a multiplier 69, the fuel flow rate (measured value) 68 is multiplied by the calorific value correction coefficient, and the result is output as the calorific value corrected fuel flow rate.

[0079] In a subtractor 71 , the calorific value corrected fuel flow rate is subtracted from the fuel flow rate demand 67 , and the result is output as a fuel flow rate command 72 .

[0080] When multiple fuels with different calorific values ​​are input and mixed, the average calorific value H of the multiple fuels in equation (6) is used instead of the calorific value 80 of the fuel in equation (2). ave may also be used.

[0081] When different types of fuels are mixed and combusted, the factors that cause the calorific value to vary increase depending on the number of types of fuel, so the calorific value correction using the fuel calorific value calculated based on the boiler efficiency η according to this embodiment becomes more effective.

[0082] FIG. 8 is a diagram illustrating calculation of fuel flow rate correction by a boiler control device in some embodiments of the present disclosure.

[0083] As shown in Fig. 8, a steam temperature setting 81, which is a control target value for the main steam temperature, and an actually measured steam temperature (measured value) 82 are input to the boiler control device 50. A subtractor 83 subtracts the steam temperature (measured value) 82 from the steam temperature setting 81, and outputs the deviation of the steam temperature. The deviation of the steam temperature is proportionally integrated by a regulator (PI controller) 84. The output value of the regulator 84 is made the fuel flow rate correction 65, and transitions to Fig. 7.

[0084] In this embodiment, instead of the estimated calorific value 73, a fuel calorific value 80 calculated based on the boiler efficiency η B or an average calorific value Have Since the calorific value correction is performed using the above, there is no need to automatically correct the estimated calorific value 73. Therefore, the calorific value adjustment circuit 70 that automatically corrects the estimated calorific value 73 shown in Fig. 6 is not required, the time required for calorific value correction in response to the fuel flow rate command 72 is significantly shortened, and it is possible to appropriately respond to fluctuations in the actual fuel calorific value.

[0085] FIG. 9 is a diagram showing a time transition of a moving average value of the calculated calorific value calculated using equation (2) or (6) in some embodiments of the present disclosure and a fuel calorific value 80 input to the control device. 9, the vertical axis represents the calculated heat generation amount moving average value or the fuel heat generation amount 80, and the horizontal axis represents time. Also, each solid line represents each value of the calculated heat generation amount moving average value or the fuel heat generation amount 80.

[0086] The calculated calorific value moving average is a time-moving average of the fuel calorific value calculated using formula (2) or formula (6). As shown in the upper diagram of Fig. 9, the calculated calorific value moving average is not a constant value but fluctuates. This is because the calculated calorific value is a value calculated based on the preset boiler efficiency ηB and each state quantity acquired by the state quantity acquisition unit 51, and therefore frequently fluctuates according to the fluctuation of each state quantity.

[0087] If the calculated calorific value, which fluctuates frequently in this way, is input as is to the control device and used as the fuel calorific value 80 to perform calorific value correction and then applied to the fuel flow rate command 72, there is a risk that the stability of the fuel flow rate control will deteriorate.

[0088] Therefore, in this embodiment, a predetermined condition is set for performing the calorific value correction, and when the predetermined condition is met, the fuel calorific value 80 is updated using the calculated calorific value, and the calorific value correction is performed. In this embodiment, the predetermined condition is when the fluctuation in the fuel calorific value continues to be equal to or greater than a first threshold value for a period of time equal to or greater than a second threshold value. Specifically, the predetermined condition is when the fluctuation in the fuel calorific value continues to be equal to or greater than X% for a period of time equal to or greater than Y minutes. For example, when the fuel is coal, it is preferable to set the condition to when the fluctuation in the fuel calorific value continues to be equal to or greater than 3% for a period of time equal to or greater than 3 minutes, but the first and second threshold values ​​can be changed as appropriate depending on the type of fuel, etc.

[0089] As shown in Fig. 9, a fluctuation in fuel calorific value occurs at time t1. Possible causes of the fluctuation in fuel calorific value include, for example, a large change in the state of the fuel, such as a change in the type of fuel supplied to the mill 31 (including, for example, differences in properties depending on the time of production even for the same type of coal) or a change in moisture content. Even if the fuel calorific value fluctuates at time t1, the fuel calorific value 80 at that time is not updated.

[0090] Next, at time t2, when a fluctuation in the fuel calorific value occurs and a fluctuation of X% or more of the amount of fluctuation in the fuel calorific value is detected for the first time, the fuel calorific value 80 is updated in accordance with the fluctuation. After that, at time t3, a further fluctuation of X% or more of the amount of fluctuation in the fuel calorific value occurs, but because the duration of the fluctuation is less than Y minutes, the fuel calorific value 80 is not updated.

[0091] Next, at time t4, if a fluctuation of X% or more in the amount of change in the fuel calorific value continues for Y minutes or more, the fuel calorific value 80 is updated using the calculated calorific value at that time. In this way, by updating the fuel calorific value 80 in a stepped manner when a predetermined condition is satisfied, excessive updates of the fuel calorific value 80 can be avoided and the stabilization of the fuel flow rate control can be improved.

[0092] In the example of FIG. 9, the fluctuation in the fuel calorific value is an increasing fluctuation, but even if the fluctuation is a decreasing fluctuation, the fuel calorific value 80 is updated in a stepwise manner when a predetermined condition is satisfied.

[0093] FIG. 10 is a control flowchart of a boiler control device in some embodiments of the present disclosure.

[0094] In step S601, the state quantity acquisition unit 51 of the boiler control device 50 acquires the state quantity of the boiler 10.

[0095] In step S602, the calculation unit 52 calculates the fuel calorific value based on the state quantity of the boiler 10 acquired by the state quantity acquisition unit 51 and the boiler efficiency.

[0096] In step S603, the boiler control device 50 judges whether or not the amount of change in the fuel calorific value calculated by the calculation unit 52 satisfies a predetermined condition. If it is judged that the amount of change in the fuel calorific value satisfies the predetermined condition (case of Y), the process proceeds to step S604. On the other hand, if it is judged that the amount of change in the fuel calorific value does not satisfy the predetermined condition (case of N), the judgment of step S603 is performed again.

[0097] In step S604, the boiler control device 50 updates the fuel calorific value 80 using the fuel calorific value calculated by the calculation unit 52, and performs calorific value correction with respect to the fuel flow rate. The control flow from step S601 to step S604 is repeatedly executed while the boiler 10 is in operation.

[0098] [Variations] In the above embodiment, an example has been described in which the boiler control device 50 uses the estimated fuel calorific value to update the fuel calorific value 80 and performs control to correct the calorific value for the fuel flow rate, but the present disclosure is not limited to this. For example, the calculated calorific value moving average value or the fuel calorific value 80 shown in Fig. 9 may be displayed on a display unit or the like to present it to an operator, and the operator may make a manual correction based on the displayed calculated calorific value moving average value or the fuel calorific value 80.

[0099] In the above embodiment, an example has been described in which the boiler control device 50 uses the calculated calorific value to update the fuel calorific value 80 and correct the calorific value when a predetermined condition is met, but the present disclosure is not limited to this. For example, when the above-mentioned predetermined condition is met, the boiler control device 50 may notify or display the operator to prompt him or her to make a manual correction.

[0100] <Additional Notes> The boiler control device, the boiler, the boiler control method, and the boiler control program described in the above-described embodiments can be understood, for example, as follows.

[0101] A boiler control device (50) of a first aspect of the present disclosure is a boiler control device that controls a boiler (10), and includes a state quantity acquisition unit (51) that acquires a state quantity of the boiler, and a calculation unit (52) that calculates a fuel calorific value, which is a calorific value of fuel input to the boiler, based on the state quantity of the boiler and a boiler efficiency that is preset in the boiler control device. When a fluctuation amount of the fuel calorific value calculated by the calculation unit satisfies a predetermined condition, a control is performed to correct the flow rate of fuel input to the boiler using the fuel calorific value.

[0102] By calculating the fuel calorific value, a quantitative index of the fuel calorific value can be obtained. In addition, since there is no need to consider the control interference of correction using the fuel flow rate and fuel calorific value, the fuel calorific value can be estimated and calculated in a shorter time.

[0103] A boiler control device of a second aspect of the present disclosure, in the first aspect, may be such that the specified condition is a case in which the fluctuation in the amount of fluctuation in the fuel calorific value continues to be equal to or greater than a first threshold value for a period of time equal to or greater than a second threshold value.

[0104] Since the correction using the fuel heat value is performed when the conditions are satisfied, the correction is not performed frequently and excessive correction can be avoided, improving the stabilization of the fuel flow rate control.

[0105] In the boiler control device of the third aspect of the present disclosure, in the first or second aspect, when a plurality of fuels with different fuel heat values ​​are input to the boiler, the calculation unit may calculate an average heat value of the plurality of fuels based on the boiler efficiency and state quantities of the boiler including a total fuel flow rate of the plurality of fuels.

[0106] By using multiple fuels with different fuel heating values, correction can be performed using the fuel heating values, and the types of fuels used in the boiler can be freely mixed and burned without any restrictions. Even when multiple fuels are used, the boiler can be stably operated and controlled. This can expand the operability of the boiler.

[0107] A boiler according to a fourth aspect of the present disclosure includes the boiler control device according to any one of the first to third aspects, and is controlled by the boiler control device.

[0108] A boiler control method (50) of a fifth aspect of the present disclosure is a boiler control method for controlling a boiler, comprising: a state quantity acquisition step of acquiring a state quantity of the boiler; and a calculation step of calculating a fuel calorific value, which is the heat value of fuel input to the boiler, based on the state quantity of the boiler and a preset boiler efficiency. When a fluctuation amount of the fuel calorific value calculated by the calculation step satisfies a predetermined condition, the method is executed by a computer that performs control to correct the fuel flow rate input to the boiler using the fuel calorific value.

[0109] A boiler control program (50) according to a sixth aspect of the present disclosure causes a computer to execute the boiler control method according to the fifth aspect. [Explanation of symbols]

[0110] 1. Power plants 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 31 Mill (Grinding Machine) 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 50 Boiler control device 51 State quantity acquisition unit 52 Calculation section 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 112 Condenser 113 Generator

Claims

1. A boiler control device that controls a boiler, a state quantity acquisition unit that acquires a state quantity of the boiler; a calculation unit that calculates a fuel calorific value, which is a calorific value of fuel input to the boiler, based on the state quantity of the boiler and a boiler efficiency that is preset in the boiler control device, When the amount of fluctuation in the fuel calorific value calculated by the calculation unit satisfies a predetermined condition, control is performed to correct the flow rate of fuel input to the boiler using the fuel calorific value, The boiler control device, wherein the predetermined condition is that the fluctuation in the amount of fluctuation in the fuel calorific value continues to be equal to or greater than a first threshold value for a period of time equal to or greater than a second threshold value.

2. 2. The boiler control device according to claim 1, wherein when a plurality of fuels with different fuel calorific values ​​are input into the boiler, the calculation unit calculates an average fuel calorific value of the plurality of fuels based on the boiler efficiency and state quantities of the boiler including a total fuel flow rate of the plurality of fuels.

3. The boiler control device according to claim 1 or 2 is provided, A boiler controlled by the boiler control device.

4. A boiler control method for controlling a boiler, comprising: a state quantity acquisition step of acquiring a state quantity of the boiler; a calculation step of calculating a fuel calorific value, which is a calorific value of fuel input to the boiler, based on the state quantity of the boiler and a preset boiler efficiency, When the amount of fluctuation in the fuel calorific value calculated in the calculation step satisfies a predetermined condition, control is performed to correct the flow rate of fuel input to the boiler using the fuel calorific value, A boiler control method executed by a computer, wherein the predetermined condition is when the fluctuation in the amount of fluctuation in the fuel calorific value continues to be equal to or greater than a first threshold value for a period of time equal to or greater than a second threshold value.

5. A boiler control program that causes a computer to execute the boiler control method according to claim 4.

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