Boiler system and method for controlling boiler

Abstract

Provided is a method for controlling a boiler. The boiler has: a furnace that is composed of a furnace wall having a plurality of heat transfer pipes through which a fluid flows; a combustion device for generating a combustion gas by injecting solid fuel and combustion air into the furnace; and a plurality of soot blowers that inject steam onto the surfaces of the heat transfer pipes, and also are capable of switching between an insertion state, in which the soot blowers are inserted into the furnace, and a pull-out state, in which the soot blowers are pulled out from the furnace. The control method comprises: a temperature detection step (S102) for detecting the temperatures of the plurality of heat transfer pipes by a plurality of temperature detection units; and a control step (S104) for controlling the operation of a predetermined soot blower, on the basis of a plurality of first temperature detection values detected by a plurality of temperature detection sensors in a first period in which the predetermined soot blower starts steam injection in the insertion state.

Description

Boiler system and boiler control method

[0001] The present disclosure relates to a boiler system and a method for controlling a boiler.

[0002] In a boiler that burns solid fuel such as pulverized coal, the powdered solid fuel is injected from a fuel burner into a furnace and burned therein. The boiler is provided with a large number of heat transfer tubes that constitute a superheater and a reheater. Ash and other materials burned during boiler operation adhere to the heat transfer tubes as clinker. If the boiler continues to operate with clinker adhered to the heat transfer tubes, the heat exchange efficiency of the heat transfer tubes decreases. Therefore, a soot blower is periodically operated to remove the clinker adhered to the heat transfer tubes (see, for example, Patent Document 1).

[0003] Patent No. 3615776

[0004] However, in Patent Document 1, the soot blower's operation interval is fixed, so it is not possible to operate the soot blower appropriately according to the amount of clinker adhering to each heat transfer tube. Even if there is a deviation in the amount of clinker adhering to each heat transfer tube, the soot blower operates at a fixed operation interval.

[0005] The present disclosure has been made in consideration of these circumstances, and aims to provide a boiler system and a boiler control method that can operate a soot blower appropriately depending on the condition of the furnace, such as the amount of clinker adhering to the heat transfer tubes.

[0006] A boiler system according to one aspect of the present disclosure comprises a boiler and a control unit that controls the boiler, wherein the boiler comprises a furnace composed of a furnace wall having a plurality of heat transfer tubes through which a fluid flows, a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gas, a plurality of soot blowers that inject steam onto the surface of the heat transfer tubes and are switchable between an inserted state in which they are inserted into the furnace and a withdrawn state in which they are withdrawn from the furnace, and a plurality of temperature detection units that detect the temperatures of the plurality of heat transfer tubes, and the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period after a predetermined soot blower starts steam injection injecting steam in the inserted state.

[0007] In one embodiment of the boiler control method of the present disclosure, the boiler has a furnace constructed of a furnace wall having a plurality of heat transfer tubes through which a fluid flows, a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gas, and a plurality of soot blowers that inject steam onto the surface of the heat transfer tubes and are switchable between an inserted state in which they are inserted into the furnace and a withdrawn state in which they are withdrawn from the furnace, and the method comprises a temperature detection process that detects the temperatures of the plurality of heat transfer tubes using a plurality of temperature detection units, and a control process that controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period after a predetermined soot blower starts steam injection to inject steam in the inserted state.

[0008] According to the present disclosure, it is possible to provide a boiler system and a boiler control method that can appropriately operate a soot blower depending on the state of the furnace, such as the amount of clinker adhering to the heat transfer tubes.

[0009] 1 is a schematic configuration diagram showing a boiler system according to an embodiment of the present disclosure. FIG. 2 is a perspective view showing a furnace according to an embodiment of the present disclosure. FIG. 3 is a cross-sectional view taken along the CC arrow in the lower region of the furnace wall shown in FIG. 2. FIG. 4 is a diagram schematically showing the structure of a soot blower. FIG. 5 is a front view of the lower region of the furnace shown in FIG. 3, viewed from the front wall. FIG. 6 is a rear view of the lower region of the furnace shown in FIG. 3, viewed from the rear wall. FIG. 7 is a right side view of the lower region of the furnace shown in FIG. 3, viewed from the right wall. FIG. 8 is a left side view of the lower region of the furnace shown in FIG. 3, viewed from the left wall. FIG. 9 is a graph showing the operating state of a soot blower and the change over time in the temperature of a heat transfer tube. FIG. 10 is a diagram showing, in sections A to D, the differential temperature value between the maximum and minimum temperature values ​​detected by multiple temperature detection units when the soot blower is operated. FIG. 11 is a diagram showing, as a grayscale image, the differential temperature value between the maximum and minimum temperature values ​​detected by multiple temperature detection units when the soot blower is operated. FIG. 12 is a flowchart showing the operation of setting a predetermined soot blower operation interval. FIG. 13 is a flowchart showing the process of operating a predetermined soot blower at a set operation interval.

[0010] 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.

[0011] 1 shows a boiler system 100 including a boiler 10 that uses pulverized fuel of this embodiment as its main fuel. The boiler system 100 includes the boiler 10 and a control unit 50 that controls the boiler 10. The boiler 10 of this embodiment is a boiler that burns pulverized fuel made from pulverized solid fuel in a combustion device and exchanges the heat generated by this combustion with feedwater or steam to generate superheated steam. Biomass fuel, coal, or the like is used as the solid fuel.

[0012] The boiler 10 has a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 has a hollow rectangular cylindrical shape and is installed vertically. The furnace 11 is formed by a furnace wall 101, which serves as the inner wall surface. The furnace wall 101 is composed of a plurality of heat transfer tubes through which fluid (water, steam) flows, and fins that connect the heat transfer tubes. The furnace wall 101 recovers heat generated by the combustion of pulverized fuel by heat exchange with the water and steam flowing inside the heat transfer tubes. The heat transfer tubes suppress a temperature rise in the furnace wall 101.

[0013] The combustion device 20 is a device that generates combustion gas by injecting solid fuel and combustion air into the furnace 11. The combustion device 20 is installed in the lower region 101A of the furnace 11. In this embodiment, the combustion device 20 has a plurality of burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, when there is no need to distinguish between these burners, they will be simply referred to as "burners 21") attached to the furnace wall 101.

[0014] The burners 21 are arranged at equal intervals in the furnace width direction along the furnace wall 101 (for example, arranged in the furnace width direction so as to face each of the opposing furnace walls 101 to achieve opposed combustion), and are arranged in multiple tiers along the vertical direction. The shape of the furnace, the number of burner tiers, the number of burners per tier, the arrangement of the burners, etc. are not limited to this embodiment.

[0015] The burners 21A, 21B, 21C, 21D, 21E, and 21F are respectively connected to a plurality of mills (pulverizers) 31A, 31B, 31C, 31D, 31E, and 31F (hereinafter, when these mills are not distinguished, they will be simply referred to as "mills 31") via a plurality of pulverized fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F (hereinafter, when these pulverized fuel supply pipes are not distinguished, they will be simply referred to as "pulverized fuel supply pipes 22").

[0016] The mill 31 is, for example, a vertical roller mill having a grinding table (not shown) supported therein so as to be rotatable, and a plurality of grinding rollers (not shown) supported above the grinding table so as to be rotatable in conjunction with the rotation of the grinding table. The solid fuel ground by the cooperation of the grinding rollers and the grinding table is transported to a classifier (not shown) provided in the mill 31 by primary air (carrier gas, oxidizing gas) supplied to the mill 31.

[0017] 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.

[0018] 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. The other end of the air duct 24 is connected to a forced draft fan (FDF) 32. Air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 and supplied to the burner 21 via the air register 23 as secondary air (combustion air, oxidizing gas) and introduced into the furnace 11.

[0019] 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, when there is no need to distinguish between these superheaters, they will simply be referred to as "superheaters 102"), reheaters 103A and 103B (hereinafter, when there is no need to distinguish between these reheaters, they will simply be referred to as "reheater 103"), and an 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 circulating inside each heat exchanger. Note that the arrangement and shape of each heat exchanger are not limited to those shown in FIG. 1.

[0020] A flue 13 is connected downstream 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.

[0021] 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, that 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.

[0022] A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is provided with environmental devices such as a dust collector 44, such as an electrostatic precipitator, that removes ash and the like from the combustion gas, a desulfurization device 46 that removes sulfur oxides, and an induced draft fan (IDF) 45 that guides the exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to a chimney 47, and the combustion gas treated in the environmental device is discharged to the outside of the system as exhaust gas.

[0023] When pulverized fuel is burned in the boiler 10, the plurality of mills 31 are driven to pulverize the solid fuel, and the pulverized fuel classified by the classifier is supplied together with primary air to the burner 21 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.

[0024] The pulverized fuel mixture injected into the furnace 11 ignites and reacts with the secondary air to form a flame. The flame is formed in a 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), but gases with a higher or lower oxygen content than air may also be used. Stable combustion in the furnace 11 can be achieved by adjusting the ratio of the oxygen content to the amount of fuel supplied within an appropriate range.

[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 height of the wind box 23) 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 amount of air (the total amount of primary air and secondary air) supplied to the burner 21 is set to be less than the theoretical air amount relative to the amount of fuel 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. Subsequently, 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 from 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 combustion 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 combustion gas is then discharged to the outside of the system through a chimney 47. 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] The control unit 50 is a device that controls each part of the boiler 10. The control unit 50 is composed of, for example, a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), and a computer-readable storage medium. A series of processes for realizing various functions is stored in the storage medium in the form of a program, for example, and the CPU reads this program into the RAM and executes information processing and arithmetic processing to realize various functions.

[0029] The program may be installed in advance in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means, etc. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

[0030] Next, a temperature detection sensor (temperature detection unit) 60 that detects the temperature of the furnace wall 101 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view showing the furnace 11 according to an embodiment of the present disclosure. Figure 3 is a cross-sectional view taken along the CC arrows of the lower region 101A of the furnace wall 101 shown in Figure 2.

[0031] 2, the furnace 11 of this embodiment is formed by a furnace wall 101 having a lower region 101A and an upper region 101B. The furnace wall 101 has a front wall 101a to which the burners 21D, 21E, and 21F of the combustion device 20 are attached, a rear wall 101b to which the burners 21A, 21B, and 21C of the combustion device 20 are attached, a right wall 101c that forms the right side of the furnace 11, and a left wall 101d that forms the left side of the furnace 11.

[0032] In FIG. 2, reference numerals 21Aa, 21Ba, 21Ca, 21Da, 21Ea, and 21F indicate positions where burners 21A, 21B, 21C, 21D, 21E, and 21F are attached, respectively.

[0033] 2, in the lower region 101A of the furnace wall 101, the heat transfer tubes 101C are formed so as to extend in a direction inclined with respect to the vertical direction VD. The heat transfer tubes 101C are formed in a spiral shape that spirals around the front wall 101a, right side wall 101c, rear wall 101b, and left side wall 101d in this order as they move along the vertical direction VD. Note that the heat transfer tubes 101C may also be formed on each of the front wall 101a, right side wall 101c, rear wall 101b, and left side wall 101d so as to extend along the vertical direction VD.

[0034] 2, the heat transfer tubes 101C are formed to extend along the vertical direction VD in the upper region 101B of the furnace wall 101. The heat transfer tubes 101C in the lower region 101A and the heat transfer tubes 101C in the upper region 101B are connected at the connection position of the lower region 101A and the upper region 101B so that a fluid (water, steam) flows continuously between them.

[0035] 3, the boiler 10 of this embodiment has a plurality of temperature detection sensors 60 for detecting the temperature of the heat transfer tubes 101C in a lower region 101A of the furnace wall 101 where the combustion device 20 is attached. Temperature detection sensors 60 for detecting the temperature T [°C] of the lower region 101A are attached to the furnace wall 101 in the lower region 101A where the burners 21A, 21B, 21C, 21D, 21E, and 21F of the combustion device 20 are attached.

[0036] As shown in FIG. 3, the boiler 10 has a plurality of temperature detection sensors (temperature detection units) 60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h, 60i, 60j, 60k, 60l, 60m, 60n, 60o, 60p, 60q, 60r, 60s, and 60t (hereinafter also referred to as temperature detection sensors 60).

[0037] Next, with reference to Figure 4, the soot blower 70 provided in the boiler 10 of this embodiment will be described. The soot blower 70 shown in Figure 4 is a device that injects steam onto the surface of the heat transfer tube 101C to remove clinker adhering to the surface of the heat transfer tube 101C and the inner wall surface of the furnace wall 101. The boiler 10 has multiple soot blowers 70 attached to the front wall 101a, rear wall 101b, right side wall 101c, and left side wall 101d, respectively. Note that although the soot blower 70 shown in Figure 4 is disposed on the furnace wall 101 of the furnace 11, other embodiments may also be used. For example, the soot blower 70 may be disposed in the combustion gas passage 12 in which the superheater 102, reheater 103, and economizer 104 are disposed.

[0038] As shown in Figure 4, the soot blower 70 includes a nozzle block 71 having spray holes 71a and 71b, a soot blower tube 72 whose tip is connected to the nozzle block 71, and a motor 73. The motor 73 and the soot blower tube 72 are connected via a power transmission mechanism (not shown) such as a gear, and rotation of the motor 73 enables the soot blower tube 72 to rotate around its central axis and move in the direction of the central axis. The soot blower 70 is switchable between an inserted state shown by a solid line in which the nozzle block 71 is inserted into the furnace 11, and a withdrawn state shown by a dotted line in which the nozzle block 71 is withdrawn to the outside of the furnace 11.

[0039] The motor 73 is driven based on commands from the control unit 50. The rear end of the soot blower tube 72 is connected to a spray steam supply line 74. The soot blower 70 circulates steam at a pressure adjusted by a steam pressure control valve 75 through the soot blower tube 72, and sprays the steam from the spray holes 71 a, 71 b into the furnace 11. By spraying steam from the spray holes 71 a, 71 b onto the heat transfer tube 101C, clinker adhering to the heat transfer tube 101C is removed.

[0040] Next, the soot blower 70 attached to the furnace wall 101 will be described with reference to Figures 5 to 8. In Figures 5 to 8, the horizontal direction is indicated by HD, and the vertical direction is indicated by VD. Note that the positions and numbers of the multiple soot blowers 70 shown in Figures 5 to 8 are merely examples, and the positions and numbers may be different from those shown in Figures 5 to 8.

[0041] Fig. 5 is a front view of the lower region 101A of the furnace 11 shown in Fig. 3, seen from the front wall 101a side. As shown in Fig. 5, soot blowers 70F1a, 70F3a, 70F5a, 70F2b, 70F4b, 70F6b, 70F1c, 70F3c, 70F5c, 70F2d, 70F4d, and 70F6d are attached to the front wall 101a. Soot blowers 70F1a, 70F3a, 70F5a, 70F2b, 70F4b, 70F6b, 70F1c, 70F3c, 70F5c, 70F2d, 70F4d, and 70F6d are mounted so as to move back and forth along axes Y1a, Y3a, Y5a, Y2b, Y4b, Y6b, Y1c, Y3c, Y5c, Y2d, Y4d, and Y6d, respectively.

[0042] Fig. 6 is a front view of the lower region 101A of the furnace 11 shown in Fig. 3 as seen from the rear wall 101b side. As shown in Fig. 6, soot blowers 70B6a, 70B4a, 70B2a, 70B5b, 70B3b, 70B1b, 70B6c, 70B4c, 70B2c, 70B5d, 70B3d, and 70B1d are attached to the rear wall 101b. Soot blowers 70B6a, 70B4a, 70B2a, 70B5b, 70B3b, 70B1b, 70B6c, 70B4c, 70B2c, 70B5d, 70B3d, and 70B1d are mounted so as to move back and forth along axes Y6a, Y4a, Y2a, Y5b, Y3b, Y1b, Y6c, Y4c, Y2c, Y5d, Y3d, and Y1d, respectively.

[0043] The axes Y1a, Y1b, Y1c, and Y1d are disposed at the position of the axis Y1 shown in Figure 3. The axes Y2a, Y2b, Y2c, and Y2d are disposed at the position of the axis Y2 shown in Figure 3. The axes Y3a, Y3b, Y3c, and Y3d are disposed at the position of the axis Y3 shown in Figure 3. The axes Y4a, Y4b, Y4c, and Y4d are disposed at the position of the axis Y4 shown in Figure 3. The axes Y5a, Y5b, Y5c, and Y5d are disposed at the position of the axis Y5 shown in Figure 3. The axes Y6a, Y6b, Y6c, and Y6d are disposed at the position of the axis Y6 shown in Figure 3.

[0044] Figure 7 is a front view of the lower region 101A of the furnace 11 shown in Figure 3, as seen from the right side wall 101c side. As shown in Figure 7, soot blowers 70R1a, 70R3a, 70R2b, 70R4b, 70R1c, 70R3c, 70R2d, and 70R4d are attached to the right side wall 101c. The soot blowers 70R1a, 70R3a, 70R2b, 70R4b, 70R1c, 70R3c, 70R2d, and 70R4d are attached so as to move forward and backward along axes X1a, X3a, X2b, X4b, X1c, X3c, X2d, and X4d, respectively.

[0045] Figure 8 is a front view of the lower region 101A of the furnace 11 shown in Figure 3, as seen from the left side wall 101d. As shown in Figure 8, soot blowers 70L4a, 70L2a, 70L3b, 70L1b, 70L4c, 70L2c, 70L3d, and 70L1d are attached to the left side wall 101d. The soot blowers 70L4a, 70L2a, 70L3b, 70L1b, 70L4c, 70L2c, 70L3d, and 70L1d are attached so as to move forward and backward along axes X4a, Y2a, X3b, X1b, X4c, X2c, X3d, and X1d, respectively.

[0046] The axes X1a, X1b, X1c, and X1d are disposed at the position of the axis X1 shown in Figure 3. The axes X2a, X2b, X2c, and X2d are disposed at the position of the axis X2 shown in Figure 3. The axes X3a, X3b, X3c, and X3d are disposed at the position of the axis X3 shown in Figure 3. The axes X4a, X4b, X4c, and X4d are disposed at the position of the axis X4 shown in Figure 3.

[0047] The control unit 50 controls the multiple soot blowers 70 attached to the front wall 101a, rear wall 101b, right side wall 101c, and left side wall 101d of the furnace wall 101 so that each is independently switched between an inserted state and a withdrawn state. Figure 9 is a graph showing the operating state of the soot blower 70 and the change in the temperature of the heat transfer tube over time. The stopped state is a state in which the nozzle block 71 of the soot blower 70 is in a withdrawn state where it is withdrawn from the furnace 11 and the driving of the motor 73 is stopped. The operating state is a state in which the motor 73 is driven to move the nozzle block 71 from the withdrawn state to the inserted state, steam is sprayed from the nozzle block 71, and then the nozzle block 71 is moved from the inserted state to the withdrawn state.

[0048] As shown in Figure 9, the control unit 50 keeps the soot blower 70 in a stopped state from time t0 to time t1, and then switches the specified soot blower 70 to an operating state at time t1. From time t1, the control unit 50 drives the motor 73 to move the soot blower tube 72 from the position shown by the dotted line in Figure 4 to the position shown by the solid line, switching the soot blower 70 from a withdrawn state to an inserted state.

[0049] In response to the soot blower insertion operation, the control unit 50 opens the steam pressure control valve 75 and sprays steam from the spray holes 71a and 71b into the furnace 11. In response to the soot blower withdrawal operation, the control unit 50 closes the steam pressure control valve 75 and stops the spraying of steam from the spray holes 71a and 71b. Thereafter, the control unit 50 drives the motor 73 from the completion of spraying until time t3 to move the soot blower tube 72 from the position shown by the solid line in Figure 4 to the position shown by the dotted line, switching the soot blower 70 from the inserted state to the withdrawn state.

[0050] 4 is configured to switch between an open state in which steam is sprayed from the spray holes 71 a, 71 b into the furnace 11 and a closed state in which steam is not sprayed from the spray holes 71 a, 71 b into the furnace 11 by a steam pressure control valve 75 arranged in the spray steam supply line 74, but other configurations are also possible. For example, a stop valve may be arranged inside the soot blower tube 72, and the stop valve may be used to switch between the open state and the closed state.

[0051] During the soot blower operation, steam is sprayed onto the heat transfer tube 101C from the spray holes 71a and 71b, thereby removing clinker adhering to the heat transfer tube 101C. As the clinker is removed, the heat transfer performance of the heat transfer tube 101C increases, and the temperature of the heat transfer tube 101C detected by the temperature detection sensor 60 increases, as shown in FIG.

[0052] The control unit 50 detects the maximum temperature value (first temperature detection value) T1 detected by the temperature detection sensor 60 during a first period PR1 from time t2 during steam injection from the spray holes 71a, 71b to time t3 when the soot blower 70 is stopped. The control unit 50 also detects the minimum temperature value (second temperature detection value) T2 detected by the temperature detection sensor 60 during a second period PR2 from time t1 when the soot blower 70 is started to time t2.

[0053] The control unit 50 calculates a differential temperature value Tdif, which is the difference obtained by subtracting the temperature value T2 from the temperature value T1. The differential temperature value Tdif is a value that indicates the degree of increase in the thermal conductivity of the heat transfer tube 101C due to the removal of clinker adhering to the heat transfer tube 101C. The larger the differential temperature value Tdif, the greater the amount of clinker that has been removed. The larger the differential temperature value Tdif calculated when a specified soot blower 70 is operated, the greater the amount of clinker that has been removed when a specified soot blower 70 is operated.

[0054] Therefore, when operating a specified soot blower 70 to perform steam injection by injecting steam onto the surface of the heat transfer tube 101C, it is effective to calculate a differential temperature value Tdif from the temperature values ​​T1 and T2 detected by multiple temperature detection sensors 60, and control the operation of the specified soot blower 70 according to the differential temperature value Tdif.

[0055] For example, by shortening the operating interval at which a given soot blower 70 performs steam injection as the differential temperature value Tdif increases, the soot blower 70 can be operated appropriately according to the state of the furnace 11 so as to remove clinker from areas where a large amount of clinker accumulates.

[0056] Here, an example of the differential temperature value Tdif calculated from the temperature values ​​T1 and T2 detected by the plurality of temperature detection sensors 60 when a given soot blower 70 performs steam injection will be described with reference to the drawings. Figure 10 is a diagram showing, in sections A to D, the differential temperature value Tdif between the maximum temperature value T1 and the minimum temperature value T2 detected by the plurality of temperature detection sensors 60 when the soot blower 70 is operated.

[0057] In Figure 10, the symbols shown in each row indicate a combination of a pair of soot blowers 70 that are simultaneously activated by the control unit 50. For example, 70F1a and 70B6a indicate that the soot blower 70F1a attached to the front wall 101a and the soot blower 70B6a attached to the rear wall 101b are simultaneously activated. Note that in the example shown in Figure 10, the soot blower 70 attached to the front wall 101a and the soot blower 70 attached to the rear wall 101b are simultaneously activated, but other embodiments are also possible. For example, the soot blower 70 attached to the front wall 101a and the soot blower 70 attached to the rear wall 101b may be activated at different times.

[0058] In Figure 10, the symbols shown in each column indicate the value of the differential temperature value Tdif calculated from the temperature values ​​T1 and T2 detected by the multiple temperature detection sensors 60 when a pair of soot blowers 70 in each row is operated. In Figure 10, A, B, C, and D each indicate the range of the differential temperature value Tdif, with the relationship A>B>C>D. For example, when soot blowers 70F1a and 70B6a are operated simultaneously, the temperature detection sensor 60n has the largest differential temperature value Tdif.

[0059] The control unit 50 stores in a memory unit (not shown) a table showing which range, A, B, C, or D, the multiple temperature detection sensors 60 and the differential temperature value Tdif shown in Figure 10 fall into. Then, as will be described later, the control unit 50 reads out the table stored in the memory unit and, when operating a pair of soot blowers 70, identifies the maximum value among the multiple differential temperature values ​​Tdif corresponding to the multiple temperature detection sensors 60, and controls the operation of the pair of soot blowers 70 based on the maximum value.

[0060] 10, the range of the differential temperature value Tdif is divided into four stages, A, B, C, and D, but other configurations are also possible. For example, the range may be divided into more than four stages, or the differential temperature value Tdif may be used as a table value directly without being divided into the stages A, B, C, and D. Furthermore, for example, instead of dividing the range into four stages, A, B, C, and D, as shown in FIG. 10, a four-stage grayscale image may be displayed on a display unit (not shown).

[0061] Figure 11 is a diagram showing, in a grayscale image, the differential temperature value Tdif between the maximum temperature value T1 and the minimum temperature value T2 detected by the multiple temperature detection sensors 60 when the soot blower 70 is operating. The image shown in four shades of gray in Figure 11 corresponds to the four ranges of differential temperature values ​​Tdif, A, B, C, and D, shown in Figure 10. The boiler 10 of this embodiment is equipped with a display unit that displays multiple differential temperature values ​​(temperature differences) Tdif in association with the temperature detection sensors 60 corresponding to each differential temperature value Tdif when a specific soot blower 70 performs steam injection.

[0062] A (the range with the largest differential temperature value Tdif) shown in Fig. 10 corresponds to the image area with the highest density in Fig. 11, and B (the range with the next largest differential temperature value Tdif after A) corresponds to the image area with the second highest density in Fig. 11. D (the range with the smallest differential temperature value Tdif) shown in Fig. 10 corresponds to the image area with the lowest density in Fig. 11, and C (the range with the next smallest differential temperature value Tdif after D) corresponds to the image area with the second lowest density in Fig. 11.

[0063] 11 on the display unit, an operator of the boiler system 100 can intuitively recognize at which position in the furnace 11 the differential temperature value Tdif becomes large (i.e., the amount of clinker removed becomes large) when steam injection is performed by a specified soot blower 70. For example, the operator can identify from the grayscale image the soot blower 70 that was operated when the differential temperature value Tdif became large (i.e., the amount of clinker removed became large), and set the control unit 50 so that the operation interval at which the identified soot blower 70 performs steam injection becomes shorter.

[0064] Next, an operation for setting a predetermined operation interval of the soot blower 70 will be described with reference to Fig. 12. Fig. 12 is a flowchart showing an operation for setting a predetermined operation interval of the soot blower 70. Each process shown in Fig. 12 is executed by the control unit 50.

[0065] In step S101, the control unit 50 controls a predetermined soot blower 70 to start operating.

[0066] In step S102, the control unit 50 detects the maximum temperature value (first temperature detection value) T1 detected by the plurality of temperature detection sensors 60 during a first period PR1 from time t2 during steam injection from the spray holes 71 a, 71 b to time t3 when the soot blower 70 is stopped. The control unit 50 also detects the minimum temperature value (second temperature detection value) T2 detected by the plurality of temperature detection sensors 60 during a second period PR2 from time t1 when the soot blower 70 is started to time t2 during steam injection from the spray holes 71 a, 71 b.

[0067] In step S103, the control unit 50 calculates a differential temperature value Tdif, which is the difference obtained by subtracting the temperature value T2 from the temperature value T1, based on the temperature values ​​T1 and T2 detected by the plurality of temperature detection sensors 60, and associates the differential temperature value Tdif with the plurality of temperature detection sensors 60. Then, the control unit 50 calculates the maximum value of the plurality of differential temperature values ​​Tdif.

[0068] In step S104, the control unit 50 sets a predetermined operation interval of the soot blower 70 based on the maximum value calculated in step S103. The control unit 50 sets the operation interval so that the operation interval becomes shorter as the maximum value increases.

[0069] In step S105, the control unit 50 controls the operation of a predetermined soot blower 70 to stop, and ends the processing of this flowchart. The control unit 50 executes the series of processes of the flowchart shown in Figure 12 for each of the multiple soot blowers 70, and sets an operating interval for each of the multiple soot blowers 70.

[0070] 12, in step S102, temperature values ​​T1 and T2 are detected, and in step S103, the differential temperature value Tdif is calculated in association with the plurality of temperature detection sensors 60. However, other configurations are also possible. For example, in step S102, only the temperature value T1 may be detected, and in step S103, the maximum value of the plurality of temperature values ​​T1 may be calculated. In this case, in step S104, the control unit 50 sets the operating interval at which a predetermined soot blower 70 performs steam injection based on the maximum value of the plurality of temperature values ​​T1.

[0071] In this case, it is preferable that the boiler 10 be equipped with a display unit that displays multiple temperature values ​​T1 in correspondence with the temperature detection sensor 60 corresponding to each temperature value T1 when a specified soot blower 70 performs steam injection.

[0072] Next, a process for operating a predetermined soot blower 70 at a set operation interval will be described with reference to Fig. 13. Fig. 13 is a flowchart showing a process for operating a predetermined soot blower 70 at a set operation interval.

[0073] In step S201, the control unit 50 controls to start the operation of a predetermined soot blower 70. In step S202, the control unit 50 controls to stop the operation of the predetermined soot blower 70.

[0074] In step S203, the control unit 50 determines whether to stop the boiler 10. If the determination is YES, the control unit 50 ends the processing of this flowchart and executes an operation to stop the boiler 10. If the determination is NO, the control unit 50 proceeds to step S204.

[0075] In step S204, the control unit 50 determines whether the predetermined operation interval of the soot blower 70 set in step S104 of Fig. 12 has elapsed, and if YES, proceeds to step S201 to again perform the predetermined operation of the soot blower 70. If NO, repeat the process of step S204.

[0076] The boiler system 100 of this embodiment described above provides the following functions and effects. According to the boiler system 100 of this embodiment, the control unit 50 controls the operation of the soot blower 70 based on multiple temperature values ​​T1 detected by multiple temperature detection sensors 60 during a first period PR1, from the start of the soot blower 70's activation to the start of steam injection. Because the first period PR1 is the period during which the soot blower 70 starts injecting steam while inserted, the temperature of the heat transfer tube 101C after clinker removal by steam injection can be detected. A higher temperature of the heat transfer tube 101C after clinker removal indicates a greater amount of clinker removal. Therefore, by controlling the operation of the soot blower 70 based on multiple temperature values ​​T1, the soot blower 70 can be operated appropriately depending on the furnace condition, such as the amount of clinker adhesion.

[0077] Furthermore, according to the boiler system 100 of this embodiment, by detecting multiple temperature values ​​T2 detected by the multiple temperature detection sensors 60 during the second period PR2, which is earlier than the first period PR1, multiple differential temperature values ​​Tdif, which are the differences between the multiple temperature values ​​T1 and the multiple temperature values ​​T2, can be calculated. Because the differential temperature value Tdif corresponds to the amount of clinker removed, the soot blower 70 can be operated appropriately depending on the state of the furnace, such as the amount of clinker adhesion.

[0078] Furthermore, according to the boiler system 100 of this embodiment, multiple differential temperature values ​​Tdif are displayed in association with the temperature detection sensors 60 corresponding to each differential temperature value Tdif, so that the operator of the boiler system 100 can intuitively recognize at which position in the furnace 11 the temperature difference becomes large (i.e., the amount of clinker removed becomes large).

[0079] Furthermore, according to the boiler system 100 of this embodiment, the first period PR1 is a period during which a predetermined soot blower 70 starts injecting steam while inserted, and therefore the plurality of temperature values ​​T1 correspond to the amount of clinker removed. Therefore, the soot blower 70 can be operated appropriately according to the state of the furnace 11, such as the amount of clinker adhesion.

[0080] According to the boiler system 100 of this embodiment, multiple temperature values ​​T1 are displayed in association with the temperature detection sensors 60 corresponding to each temperature value T1, so that the operator of the boiler system 100 can intuitively recognize at which position in the furnace 11 the temperature difference becomes larger (i.e., the amount of clinker removed becomes larger).

[0081] [Other embodiments] In the above description, the boiler system 100 has multiple temperature detection sensors 60 that detect the temperatures of multiple heat transfer tubes 101C, and the control unit 50 controls the operation of a specified soot blower 70 based on multiple temperature values ​​(first temperature detection values) detected by the multiple temperature detection sensors 60 during the first period PR1 in which a specified soot blower 70 starts injecting steam while inserted, but other embodiments may also be used.

[0082] For example, the boiler system 100 may have a plurality of temperature detection sensors that detect the temperature of the combustion gas flowing through the combustion gas passage 12, and the control unit 50 may control the operation of a specified soot blower based on a plurality of temperature values ​​(first temperature detection values) detected by the plurality of temperature detection sensors during a first period PR1 in which a specified soot blower starts steam injection in an inserted state.

[0083] In this case, the multiple soot blowers inject steam into heat exchangers (superheater 102, reheater 103, economizer 104) arranged in the combustion gas passage 12, and are switchable between an inserted state in which they are inserted into the combustion gas passage 12 and a withdrawn state in which they are withdrawn from the combustion gas passage 12.

[0084] When a predetermined soot blower is operated to perform steam injection to inject steam onto the surface of the heat exchanger, the control unit 50 calculates a differential temperature value Tdif from the combustion gas temperature values ​​T1 and T2 detected by the multiple temperature detection sensors, and controls the operation of the predetermined soot blower according to the differential temperature value Tdif. For example, by shortening the operating interval at which the predetermined soot blower performs steam injection as the differential temperature value Tdif increases, the soot blower 70 can be operated appropriately according to the state of the combustion gas passage 12 so as to remove clinker from areas where a large amount of clinker accumulates.

[0085] The boiler system and the boiler control method described in each of the above-described embodiments can be understood, for example, as follows.

[0086] The boiler system according to the first aspect of the present disclosure comprises a boiler (10) and a control unit (50) for controlling the boiler, wherein the boiler comprises a furnace (11) composed of a furnace wall (101) having a plurality of heat transfer tubes through which a fluid flows, a combustion device (20) for injecting solid fuel and combustion air into the furnace to generate combustion gas, a plurality of soot blowers (70) for injecting steam onto the surface of the heat transfer tubes and capable of switching between an inserted state in which the blowers are inserted into the furnace and an extracted state in which the blowers are extracted from the furnace, and a plurality of temperature detection units (60) for detecting the temperatures of the plurality of heat transfer tubes, and the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period (PR1) in which a predetermined soot blower starts steam injection to inject steam in the inserted state.

[0087] According to the boiler system of the first aspect of the present disclosure, the control unit controls the operation of the predetermined soot blower based on a plurality of first temperature detection values ​​detected by a plurality of temperature detection units during a first period (PR1) in which the predetermined soot blower starts steam injection while inserted. Because the first period is the period in which the predetermined soot blower starts steam injection while inserted, the control unit can detect the temperature of the heat transfer tube after clinker has been removed by steam injection. A higher temperature of the heat transfer tube after clinker removal indicates a greater amount of clinker removal. Therefore, by controlling the operation of the predetermined soot blower based on a plurality of first temperature detection values, the soot blower can be operated appropriately according to the furnace condition, such as the amount of clinker adhesion.

[0088] A boiler system according to a second aspect of the present disclosure is the first aspect, further including the following configuration. That is, the control unit controls the operation interval at which the predetermined soot blower performs the steam injection based on multiple temperature differences, which are the differences between the multiple temperature detection values ​​and multiple second temperature detection values ​​detected by the multiple temperature detection units during a second period (PR2) prior to the first period (PR1). According to the boiler system according to the second aspect of the present disclosure, multiple temperature differences, which are the differences between the multiple first temperature detection values ​​and the multiple second temperature detection values, can be calculated by detecting multiple second temperature detection values ​​detected by the multiple temperature detection units during the second period prior to the first period. Since these temperature differences correspond to the amount of clinker removed, the soot blower can be operated appropriately depending on the state of the furnace, such as the amount of clinker adhesion.

[0089] The boiler system according to the third aspect of the present disclosure is the second aspect, further comprising the following configuration: the first temperature detection value is the maximum temperature value detected by the temperature detection unit in the first period, and the second temperature detection value is the minimum temperature value detected by the temperature detection unit in the second period. According to the boiler system according to the third aspect of the present disclosure, the soot blower can be operated appropriately based on the difference between the maximum temperature value detected by the temperature detection unit in the first period and the minimum temperature value detected by the temperature detection unit in the second period.

[0090] The boiler system according to a fourth aspect of the present disclosure is the second or third aspect, further comprising the following configuration: a display unit that displays the plurality of temperature differences associated with the temperature detectors corresponding to each of the temperature differences when the predetermined soot blower performs the steam injection. According to the boiler system according to the fourth aspect of the present disclosure, the plurality of temperature differences are displayed in association with the temperature detectors corresponding to each of the temperature differences, allowing the operator of the boiler system to intuitively recognize at which position in the furnace the temperature difference becomes large (i.e., the amount of clinker removed becomes large).

[0091] The boiler system according to the fifth aspect of the present disclosure is the first aspect, further comprising the following configuration. That is, the control unit controls the operating interval at which the specified soot blower performs the steam injection based on the multiple first temperature detection values. According to the boiler system according to the fifth aspect of the present disclosure, since the first period is the period during which the specified soot blower starts steam injection while in an inserted state, the multiple first temperature detection values ​​correspond to the amount of clinker removed. Therefore, the soot blower can be operated appropriately depending on the state of the furnace, such as the amount of clinker adhesion.

[0092] A boiler system according to a sixth aspect of the present disclosure is the fifth aspect, further comprising the following configuration: the first temperature detection value is a temperature value detected by the temperature detection unit during the first period. According to the boiler system according to the sixth aspect of the present disclosure, the soot blower can be operated appropriately based on the temperature value detected by the temperature detection unit during the first period.

[0093] A boiler system according to a seventh aspect of the present disclosure is the fifth or sixth aspect, further comprising the following configuration: a display unit that displays the plurality of first temperature detection values ​​in association with the temperature detection units corresponding to each of the first temperature detection values ​​when the predetermined soot blower performs the steam injection. According to the boiler system according to the seventh aspect of the present disclosure, the plurality of first temperature detection values ​​are displayed in association with the temperature detection units corresponding to each of the first temperature detection values, allowing an operator of the boiler system to intuitively recognize at which position in the furnace the temperature difference becomes larger (i.e., the amount of clinker removed becomes larger).

[0094] In a boiler control method relating to an eighth aspect of the present disclosure, the boiler has a furnace constructed of a furnace wall having a plurality of heat transfer tubes through which a fluid flows, a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gas, and a plurality of soot blowers that inject steam onto the surface of the heat transfer tubes and are switchable between an inserted state in which they are inserted into the furnace and a withdrawn state in which they are withdrawn from the furnace, and is equipped with a temperature detection process (S102) that detects the temperatures of the plurality of heat transfer tubes using a plurality of temperature detection units, and a control process (S104) that controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period in which a predetermined soot blower starts steam injection in the inserted state.

[0095] According to the boiler control method of the eighth aspect of the present disclosure, the control step controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by a plurality of temperature detection units during a first period after the predetermined soot blower starts injecting steam in an inserted state. Since the first period is the period after the predetermined soot blower starts injecting steam in an inserted state, the temperature of the heat transfer tube after clinker has been removed by steam injection can be detected. A higher temperature of the heat transfer tube after clinker removal indicates a greater amount of clinker removal. Therefore, by controlling the operation of the predetermined soot blower based on a plurality of first temperature detection values, the soot blower can be operated appropriately depending on the state of the furnace, such as the amount of clinker adhesion.

[0096] A boiler system according to a ninth aspect of the present disclosure comprises a boiler and a control unit that controls the boiler, wherein the boiler has a furnace, a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gas, a combustion gas passage through which the combustion gas generated by the combustion device flows, a heat exchanger that is arranged in the combustion gas passage and recovers heat from the combustion gas, a plurality of soot blowers that inject steam into the heat exchanger and are switchable between an inserted state inserted into the combustion gas passage and a withdrawn state withdrawn from the combustion gas passage, and a plurality of temperature detection units that detect the temperature of the combustion gas flowing through the combustion gas passage, and the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period in which a predetermined soot blower starts steam injection in the inserted state.

[0097] According to a boiler system according to a ninth aspect of the present disclosure, the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by a plurality of temperature detection units during a first period in which the predetermined soot blower starts steam injection while inserted. Because the first period is the period in which the predetermined soot blower starts steam injection while inserted, the temperature of the heat transfer tube after clinker removal by steam injection can be detected. The lower the temperature of the combustion gas after clinker removal, the greater the amount of clinker removed. Therefore, by controlling the operation of the predetermined soot blower based on a plurality of first temperature detection values, the soot blower can be operated appropriately according to the state of the furnace, such as the amount of clinker adhesion.

[0098] REFERENCE SIGNS LIST 10 Boiler 11 Furnace 20 Combustion device 21 Burner 31 Mill 50 Control unit 60 Temperature detection sensor 70 Soot blower 71 Nozzle block 71a, 71b Spray holes 72 Soot blower tube 73 Motor 74 Spray steam supply line 75 Steam pressure control valve 100 Boiler system 101 Furnace wall 101C Heat transfer tube VD Vertical direction PR1 First period PR2 Second period

Claims

1. A boiler system comprising: a boiler; and a control unit for controlling the boiler, wherein the boiler comprises: a furnace composed of a furnace wall having a plurality of heat transfer tubes through which a fluid flows; a combustion device for injecting solid fuel and combustion air into the furnace to generate combustion gas; a plurality of soot blowers for injecting steam onto the surfaces of the heat transfer tubes and capable of switching between an inserted state in which it is inserted into the furnace and a withdrawn state in which it is withdrawn from the furnace; and a plurality of temperature detection units for detecting the temperatures of the plurality of heat transfer tubes, wherein the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period in which a predetermined soot blower starts steam injection in the inserted state.

2. The boiler system of claim 1, wherein the control unit controls the operating interval at which the specified soot blower performs the steam injection based on a plurality of temperature differences which are the differences between a plurality of the first temperature detection values ​​and a plurality of second temperature detection values ​​detected by a plurality of the temperature detection units during a second period prior to the first period.

3. A boiler system as described in claim 2, wherein the first temperature detection value is the maximum temperature value detected by the temperature detection unit during the first period, and the second temperature detection value is the minimum temperature value detected by the temperature detection unit during the second period.

4. A boiler system as described in claim 2 or claim 3, further comprising a display unit which displays a plurality of the temperature differences in correspondence with the temperature detection unit corresponding to each of the temperature differences when the specified soot blower performs the steam injection.

5. A boiler system as described in claim 1, wherein the control unit controls the operation interval at which the specified soot blower performs the steam injection based on a plurality of the first temperature detection values.

6. A boiler system as described in claim 5, wherein the first temperature detection value is a maximum temperature value detected by the temperature detection unit during the first period.

7. A boiler system as described in claim 5 or claim 6, further comprising a display unit which displays a plurality of the first temperature detection values ​​in correspondence with the temperature detection units corresponding to each of the first temperature detection values ​​when the specified soot blower performs the steam injection.

8. A method for controlling a boiler, the boiler having: a furnace composed of a furnace wall having a plurality of heat transfer tubes through which a fluid flows; a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gas; and a plurality of soot blowers that inject steam onto the surfaces of the heat transfer tubes and are switchable between an inserted state in which they are inserted into the furnace and an extracted state in which they are extracted from the furnace, the method comprising: a temperature detection process for detecting the temperatures of the plurality of heat transfer tubes by a plurality of temperature detection units; and a control process for controlling the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period in which a predetermined soot blower starts steam injection in the inserted state.

9. A boiler system comprising: a boiler; and a control unit for controlling the boiler, the boiler having: a furnace; a combustion device for injecting solid fuel and combustion air into the furnace to generate combustion gas; a combustion gas passage for circulating the combustion gas generated by the combustion device; a heat exchanger disposed in the combustion gas passage for recovering heat from the combustion gas; a plurality of soot blowers for injecting steam into the heat exchanger and capable of switching between an inserted state in which the soot blower is inserted into the combustion gas passage and an extracted state in which the soot blower is extracted from the combustion gas passage; and a plurality of temperature detection units for detecting the temperature of the combustion gas flowing through the combustion gas passage, wherein the control unit controls the operation of a predetermined soot blower based on a plurality of first temperature detection values ​​detected by the plurality of temperature detection units during a first period in which a predetermined soot blower starts steam injection in the inserted state.

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