Boiler system and method for controlling boiler

Abstract

Provided is a boiler system comprising a boiler and a control unit that controls the boiler. The boiler has: a furnace (11) configured from a furnace wall (101) having a heat transfer pipe through which a fluid flows; a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace (11); a first temperature detection unit for detecting a first temperature of a lower region (101A), of the furnace wall (101), to which the combustion device is attached; and a second temperature detection unit for detecting a second temperature of an upper region (101B), of the furnace wall (101), that is disposed above the lower region (101A) and to which the combustion device is not attached. The control unit controls the boiler on the basis of the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

Description

Boiler system and boiler control method

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

[0002] Conventionally, coal-fired boilers that switch between different coal types with different properties are known (see, for example, Patent Document 1). Patent Document 1 discloses that in a coal-fired boiler that switches between different coal types with different properties, a change in the operating data of a coal mill is detected to determine the change in coal type for a coal bunker, and the setting of the boiler control mechanism is changed to the new coal type setting. Patent Document 1 also discloses that a change in combustion data, such as the heat quantity in the boiler, the temperature distribution in the boiler, and the boiler efficiency, is detected to determine the change in coal type for the coal bunker that has the shortest remaining coal consumption time at that time.

[0003] Japanese Patent Application Laid-Open No. 2007-315636

[0004] In Patent Document 1, although it is possible to detect changes in the operation data and combustion data of the coal mill and determine whether the coal type in the coal bunker has been switched, it is not possible to directly set the boiler control mechanism based on the detection results of changes in the operation data and combustion data of the coal mill.The coal-fired boiler in Patent Document 1 is equipped with a storage means that stores property data such as calorific value and mass for each coal type, and allows an operator to change the property data of the switched coal type by inputting the number of the switched coal type in advance.

[0005] That is, in Patent Document 1, although the timing of the coal type switch can be detected from changes in the operation data and combustion data of the coal mill, the coal type after the switch and the settings of the boiler control mechanism for that coal type must be made in advance by the operator of the coal-fired boiler. Therefore, in Patent Document 1, the operator must recognize in advance what coal type the coal type in the coal bunker will be switched to and input the coal type number, etc. as settings for the boiler control mechanism.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a boiler system and a boiler control method that can appropriately control the boiler in accordance with changes in the properties of solid fuel supplied to a combustion device without requiring operator operation when the properties of the solid fuel change.

[0007] 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 formed by a furnace wall having heat transfer tubes through which a fluid flows, a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace, a first temperature detection unit that detects a first temperature in a lower region of the furnace wall where the combustion device is attached, and a second temperature detection unit that detects a second temperature in an upper region of the furnace wall where the combustion device is not attached and is located above the lower region, and the control unit controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

[0008] In a boiler control method according to one aspect of the present disclosure, the boiler comprises: a furnace configured by a furnace wall having heat transfer tubes through which a fluid flows; a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace; a first temperature detection step of detecting a first temperature in a lower region of the furnace wall where the combustion device is attached; a second temperature detection step of detecting a second temperature in an upper region of the furnace wall where the combustion device is not attached and which is located above the lower region; and a control step of controlling the boiler based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

[0009] According to the present disclosure, it is possible to provide a boiler system and a boiler control method that can appropriately control the boiler in accordance with changes in the properties of the solid fuel supplied to the combustion device, without requiring operator operation, even when the properties of the solid fuel change.

[0010] Fig. 2 is a schematic configuration diagram showing a boiler system according to an embodiment of the present disclosure. Fig. 3 is a perspective view showing a furnace according to an embodiment of the present disclosure. Fig. 4 is a cross-sectional view taken along the arrows CC in the lower region of the furnace wall shown in Fig. 2. Fig. 5 is a cross-sectional view taken along the arrows DD in the upper region of the furnace wall shown in Fig. 2. Fig. 6 is a flowchart showing a boiler control method according to an embodiment of the present disclosure.

[0011] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to this embodiment, and when there are multiple embodiments, it also includes configurations that combine the embodiments. In the following description, "up" and "upper" refer to the upper side in the vertical direction, and "lower" and "lower" refer to the lower side in the vertical direction, and the vertical direction is not precise and may include errors.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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").

[0017] 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.

[0018] 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.

[0019] 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.

[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, 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Next, the first temperature detection unit 60 and the second temperature detection unit 70 that detect the temperature of the furnace wall 101 will be described with reference to Figures 2 to 4. Figure 2 is a perspective view showing a furnace 11 according to one embodiment of the present disclosure. Figure 3 is a cross-sectional view taken along the arrows C-C of the lower region 101A of the furnace wall 101 shown in Figure 2. Figure 4 is a cross-sectional view taken along the arrows D-D of the upper region 101B of the furnace wall 101 shown in Figure 2. Note that the furnace 11 and furnace wall 101 shown in Figures 2 to 4 are examples, and various modifications are possible to the shapes of the furnace 11 and furnace wall 101.

[0032] 2 to 4, 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 3, the boiler 10 of this embodiment has a first temperature detection unit 60 that detects a first temperature T1 in a lower region 101A of the furnace wall 101 to which the combustion device 20 is attached. The first temperature detection unit 60 that detects the first temperature T1 [°C] in the lower region 101A is attached to the furnace wall 101 to which the burners 21A, 21B, 21C, 21D, 21E, and 21F of the combustion device 20 are attached.

[0037] 3, the first temperature detection unit 60 has a plurality of first temperature detection sensors 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 first temperature detection sensors 60a to 60t). The first temperature detection unit 60 detects, for example, the average value of the temperatures output from the first temperature detection sensors 60a to 60t as a first temperature T1 [°C].

[0038] In addition, the first temperature detection unit 60 may detect the first temperature T1 using a predetermined calculation method based on the temperatures output from the first temperature detection sensors 60a to 60t, such as the highest temperature among the temperatures output from the first temperature detection sensors 60a to 60t, or the median of the standard deviation of the temperatures output from the first temperature detection sensors 60a to 60t.

[0039] 4, the boiler 10 of this embodiment has a second temperature detection unit 70 that detects a second temperature T2 in an upper region 101B of the furnace wall 101, where the combustion device 20 is not installed and where the upper region 101B is located above the lower region 101A. The second temperature detection unit 70 that detects the second temperature T2 [°C] of the upper region 101B is installed in the furnace wall 101, where the burners 21A, 21B, 21C, 21D, 21E, 21F of the combustion device 20 are not installed.

[0040] 3, the second temperature detection unit 70 has a plurality of second temperature detection sensors 70a, 70b, 70c, 70d, 70e, 70f, 70g, 70h, 70i, 70j, 70k, 70l, 70m, 70n, 70o, 70p, 70q, 70r, 70s, and 70t (hereinafter also referred to as second temperature detection sensors 70a to 70t). The second temperature detection unit 70 detects, for example, the average value of the temperatures output from the second temperature detection sensors 70a to 70t as the second temperature T2 [°C].

[0041] In addition, the second temperature detection unit 70 may detect the second temperature T2 using a predetermined calculation method based on the temperatures output from the second temperature detection sensors 70a to 70t, such as the highest temperature among the temperatures output from the second temperature detection sensors 70a to 70t, or the median of the standard deviation of the temperatures output from the second temperature detection sensors 70a to 70t.

[0042] Next, a method for controlling the boiler 10 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing a method for controlling the boiler 10 according to an embodiment of the present disclosure. The control unit 50 executes a control program to perform the processes shown in Fig. 5. The processes shown in Fig. 5 are processes executed by the control unit 50 while the boiler 10 is in operation.

[0043] In step S101, the control unit 50 acquires the first temperature T1 of the lower region 101A of the furnace wall 101 detected by the first temperature detection unit 60 from the first temperature detection unit 60. In response to receiving a control command to detect the first temperature T1 from the control unit 50, the first temperature detection unit 60 transmits the first temperature T1 of the lower region 101A of the furnace wall 101 to the control unit 50.

[0044] In step S102, the control unit 50 acquires the second temperature T2 of the upper region 101B of the furnace wall 101 detected by the second temperature detection unit 70 from the second temperature detection unit 70. In response to receiving a control command from the control unit 50 to detect the second temperature T2, the second temperature detection unit 70 transmits the second temperature T2 of the upper region 101B of the furnace wall 101 to the control unit 50.

[0045] In step S103, the control unit 50 determines whether the temperature difference obtained by subtracting the first temperature T1 from the second temperature T2 is higher than a predetermined temperature Ta, and if the answer is YES, proceeds to step S104, and if the answer is NO, proceeds to step S105.

[0046] In step S104, the control unit 50 estimates that the type of solid fuel is low-fuel-ratio coal because the temperature difference obtained by subtracting the first temperature T1 from the second temperature T2 is higher than the predetermined temperature Ta.

[0047] In step S105, the control unit 50 determines whether the temperature difference obtained by subtracting the first temperature T1 from the second temperature T2 is lower than a predetermined temperature Tb, and if the answer is YES, the process proceeds to step S106, and if the answer is NO, the process proceeds to step S107.

[0048] In this embodiment, the temperature difference between the first temperature T1 and the second temperature T2 when multiple types of solid fuels are burned is obtained in advance, and the predetermined temperatures Ta and Tb are set by associating the type of solid fuel with the temperature difference between the first temperature T1 and the second temperature T2 obtained in advance. For example, the temperature difference between the first temperature T1 and the second temperature T2 when three types of solid fuels are burned, in descending order of fuel ratio of the solid fuel, namely, high fuel ratio, medium fuel ratio, and low fuel ratio, is obtained in advance.

[0049] Then, the predetermined temperature Tb is set to a value between the temperature difference between the first temperature T1 and the second temperature T2 when a solid fuel with a high fuel ratio is combusted and the temperature difference between the first temperature T1 and the second temperature T2 when a solid fuel with a medium fuel ratio is combusted. Also, the predetermined temperature Ta is set to a value between the temperature difference between the first temperature T1 and the second temperature T2 when a solid fuel with a medium fuel ratio is combusted and the temperature difference between the first temperature T1 and the second temperature T2 when a solid fuel with a low fuel ratio is combusted.

[0050] In step S106, the control unit 50 estimates that the type of solid fuel is high-fuel-ratio coal because the temperature difference obtained by subtracting the first temperature T1 from the second temperature T2 is lower than the predetermined temperature Tb.

[0051] In step S107, the control unit 50 estimates that the type of solid fuel is medium fuel ratio coal because the temperature difference obtained by subtracting the first temperature T1 from the second temperature T2 is below the predetermined temperature Ta and above the predetermined temperature Tb.

[0052] In step S108, the control unit 50 estimates the fuel ratio of the solid fuel based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70, and sets control parameters for controlling the boiler 10 based on the fuel ratio. After setting the control parameters, the control unit 50 controls the boiler 10 based on the set control parameters.

[0053] Here, the control parameters of the boiler 10 refer to various parameters that affect the operating characteristics of the boiler 10, such as the flow rate setting of the superheater spray valve of the superheater 102. Also, the control parameters of the boiler 10 refer to, for example, the spray flow rate for controlling the superheater spray valve to an appropriate temperature relative to the main steam temperature. The control unit 50 estimates the fuel ratio of the solid fuel based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70, and controls the operation of the superheater spray valve based on the fuel ratio.

[0054] In addition to the flow rate setting of the superheater spray valve, the control parameters include parameters for stabilizing boiler operation according to the load (such as the set values ​​of the outlet and inlet temperatures of each heat transfer tube), and these control parameters are switched depending on the type of solid fuel.

[0055] 5, the control unit 50 estimates the fuel ratio of the solid fuel based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70, and sets the control parameters for controlling the boiler 10 based on the fuel ratio, but other configurations are also possible. For example, the control unit 50 may directly set the control parameters for controlling the boiler 10 based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70.

[0056] For example, when controlling the flow rate of the superheater spray valve of the superheater 102 as a control parameter, the predicted main steam temperature is associated in advance with the temperature difference between the first temperature T1 and the second temperature T2, and the spray flow rate is determined from the temperature difference. Also, for other control parameters (e.g., the outlet temperature and inlet temperature of each heat transfer tube, etc.), the set values ​​of the control parameters are associated in advance with the temperature difference between the first temperature T1 and the second temperature T2, and the set values ​​of the control parameters are determined from the temperature difference.

[0057] The boiler system 100 of this embodiment described above provides the following actions and effects. According to the boiler system of this embodiment, a first temperature in a lower region of the furnace wall where the combustion device is installed is detected by the first temperature detection unit, and a second temperature in an upper region of the furnace wall where the combustion device is not installed and is located above the lower region is detected by the second temperature detection unit. The inventors have newly discovered that the larger the temperature difference obtained by subtracting the first temperature from the second temperature, the lower the fuel ratio of the solid fuel, and the smaller the temperature difference obtained by subtracting the first temperature from the second temperature, the higher the fuel ratio of the solid fuel.

[0058] According to the boiler system 100 of this embodiment, the boiler 10 is controlled based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70. Because the temperature difference corresponds to the fuel ratio of the solid fuel, the boiler 10 can be appropriately controlled in response to changes in the properties of the solid fuel without requiring any operation by an operator.

[0059] Furthermore, according to the boiler system 100 of this embodiment, the fuel ratio of the solid fuel can be estimated based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70, and the boiler 10 can be appropriately controlled based on the fuel ratio.

[0060] Furthermore, according to the boiler system 100 of this embodiment, the boiler 10 can be appropriately controlled based on the fuel ratio estimated based on the temperature difference between the first temperature T1 detected by the first temperature detection unit 60 and the second temperature T2 detected by the second temperature detection unit 70.

[0061] Furthermore, according to the boiler system 100 of this embodiment, the boiler 10 can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between the first temperature T1 in the lower region 101A of the furnace wall 101 and the second temperature T2 in the upper region 101B of the furnace wall 101, where the heat transfer tubes are formed to extend along the vertical direction VD.

[0062] Furthermore, according to the boiler system 100 of this embodiment, the boiler 10 can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between the first temperature T1 in the lower region 101A of the furnace wall 101, where the heat transfer tubes are formed along the vertical direction, and the second temperature T2 in the upper region 101B of the furnace wall 101, where the heat transfer tubes are formed to extend along the vertical direction VD.

[0063] The boiler system and the boiler control method described in each of the above-described embodiments can be understood, for example, as follows.

[0064] A boiler system according to a first aspect of the present disclosure comprises a boiler (10) and a control unit (50) that controls the boiler, wherein the boiler comprises a furnace (11) constituted by a furnace wall (101) having heat transfer tubes through which a fluid flows, a combustion device (20) that injects solid fuel and combustion air into the furnace to generate combustion gas, a first temperature detection unit (60) that detects a first temperature (T1) in a lower region (101A) of the furnace wall to which the combustion device is attached, and a second temperature detection unit (70) that detects a second temperature (T2) in an upper region (101B) of the furnace wall to which the combustion device is not attached and which is located above the lower region, and the control unit controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

[0065] According to the boiler system of the first aspect of the present disclosure, a first temperature of a lower region of the furnace wall where the combustion device is installed is detected by a first temperature detection unit, and a second temperature of an upper region of the furnace wall where the combustion device is not installed and is located above the lower region is detected by a second temperature detection unit. The inventors have newly discovered that the larger the temperature difference obtained by subtracting the first temperature from the second temperature, the lower the fuel ratio of the solid fuel, and the smaller the temperature difference obtained by subtracting the first temperature from the second temperature, the higher the fuel ratio of the solid fuel.

[0066] According to the boiler system of the first aspect of the present disclosure, the boiler is controlled based on the temperature difference between the first temperature detected by the first temperature detector and the second temperature detected by the second temperature detector. Because the temperature difference corresponds to the fuel ratio of the solid fuel, the boiler can be appropriately controlled in response to changes in the properties of the solid fuel without requiring operator operation.

[0067] The boiler system according to the second aspect of the present disclosure is the same as the first aspect, but further includes the following configuration. That is, the control unit estimates the fuel ratio of the solid fuel based on the temperature difference and controls the boiler based on the fuel ratio. According to the boiler system according to the second aspect of the present disclosure, the fuel ratio of the solid fuel can be estimated based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit, and the boiler can be appropriately controlled based on the fuel ratio.

[0068] A boiler system according to a third aspect of the present disclosure is the second aspect, further comprising the following configuration: the boiler includes a superheater having a superheater spray valve, and the control unit controls the operation of the superheater spray valve based on the fuel ratio. According to the boiler system according to the third aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel by controlling the operation of the superheater spray valve based on the fuel ratio estimated based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

[0069] A boiler system according to a fourth aspect of the present disclosure is any one of the first to third aspects, further comprising the following configuration: In the lower region of the furnace wall, the heat transfer tubes are spirally formed so as to extend in a direction inclined with respect to the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed so as to extend along the vertical direction. According to the boiler system according to the fourth aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between a first temperature in the lower region of the furnace wall where the heat transfer tubes are spirally formed and a second temperature in the upper region of the furnace wall where the heat transfer tubes are formed so as to extend along the vertical direction.

[0070] A boiler system according to a fifth aspect of the present disclosure is any one of the first to third aspects, further comprising the following configuration: In the lower region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction. According to the boiler system according to the fifth aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between a first temperature in the lower region of the furnace wall where the heat transfer tubes are formed to extend along the vertical direction and a second temperature in the upper region of the furnace wall where the heat transfer tubes are formed to extend along the vertical direction.

[0071] In a boiler control method according to a sixth aspect of the present disclosure, the boiler has a furnace configured with a furnace wall having heat transfer tubes through which a fluid flows, and a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace, and is equipped with a first temperature detection step of detecting a first temperature in a lower region of the furnace wall where the combustion device is attached, a second temperature detection step of detecting a second temperature in an upper region of the furnace wall where the combustion device is not attached and which is located above the lower region, and a control step of controlling the boiler based on the temperature difference between the first temperature detected by the first temperature detection step and the second temperature detected by the second temperature detection step.

[0072] According to the boiler control method of the sixth aspect of the present disclosure, a first temperature of a lower region of the furnace wall where a combustion device is attached is detected in a first temperature detection step, and a second temperature of an upper region of the furnace wall where a combustion device is not attached and is disposed above the lower region is detected in a second temperature detection step. The inventors have newly discovered that the larger the temperature difference obtained by subtracting the first temperature from the second temperature, the lower the fuel ratio of the solid fuel, and the smaller the temperature difference obtained by subtracting the first temperature from the second temperature, the higher the fuel ratio of the solid fuel.

[0073] According to the boiler control method of the sixth aspect of the present disclosure, the boiler is controlled based on the temperature difference between the first temperature detected in the first temperature detection step and the second temperature detected in the second temperature detection step. Because the temperature difference corresponds to the fuel ratio of the solid fuel, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel without requiring operator operation.

[0074] A boiler control method according to a seventh aspect of the present disclosure is the sixth aspect, further comprising the following configuration. That is, the control step estimates a fuel ratio of the solid fuel based on the temperature difference, and controls the boiler based on the fuel ratio. According to the boiler control method according to the seventh aspect of the present disclosure, the fuel ratio of the solid fuel is estimated based on the temperature difference between the first temperature detected in the first temperature detection step and the second temperature detected in the second temperature detection step, and the boiler can be appropriately controlled based on the fuel ratio.

[0075] A boiler control method according to an eighth aspect of the present disclosure is the same as the seventh aspect, further comprising the following configuration: the boiler includes a superheater having a superheater spray valve, and the control step controls operation of the superheater spray valve based on the fuel ratio. According to the boiler control method according to the eighth aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel by controlling operation of the superheater spray valve based on the fuel ratio estimated based on the temperature difference between the first temperature detected in the first temperature detection step and the second temperature detected in the second temperature detection step.

[0076] A boiler control method according to a ninth aspect of the present disclosure is the same as any of the sixth to eighth aspects, further comprising the following configuration: In the lower region of the furnace wall, the heat transfer tubes are spirally formed so as to extend in a direction inclined with respect to the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed so as to extend along the vertical direction. According to the boiler control method according to the ninth aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between a first temperature in the lower region of the furnace wall where the heat transfer tubes are spirally formed and a second temperature in the upper region of the furnace wall where the heat transfer tubes are formed so as to extend along the vertical direction.

[0077] A boiler control method according to a tenth aspect of the present disclosure is the same as any of the sixth to eighth aspects, further comprising the following configuration: In the lower region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction. According to the boiler control method according to the tenth aspect of the present disclosure, the boiler can be appropriately controlled in accordance with changes in the properties of the solid fuel based on the temperature difference between a first temperature in the lower region of the furnace wall where the heat transfer tubes are formed to extend along the vertical direction and a second temperature in the upper region of the furnace wall where the heat transfer tubes are formed to extend along the vertical direction.

[0078] DESCRIPTION OF SYMBOLS 10 Boiler 11 Furnace 12 Combustion gas passage 13 Flue 20 Combustion device 21, 21A, 21B, 21C, 21D, 21E, 21F Burner 22, 22A, 22B, 22C, 22D, 22E, 22F Pulverized fuel supply pipe 23 Wind box 24 Wind duct 25 Additional air port 26 Additional air duct 31 Mill 32 Forced draft fan 41 Gas duct 42 Air preheater 43 Denitrification device 44 Device 46 Desulfurization device 47 Chimney 50 Control unit 60 First temperature detection unit 60a to 60t First temperature detection sensor 70 Second temperature detection unit 70a to 70t Second temperature detection sensor 100 Boiler system 101 Furnace wall 101A Lower area 101B Upper area 101C Heat exchanger tube 101a Front wall 101b Rear wall 101c Right side wall 101d Left side wall 102, 102A, 102B, 102C Superheater 103, 103A, 103B Reheater 104 Energy saver VD Vertical direction

Claims

1. A boiler system comprising: a boiler; and a control unit that controls the boiler, wherein the boiler comprises: a furnace composed of a furnace wall having heat transfer tubes through which a fluid flows; a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace; a first temperature detection unit that detects a first temperature in a lower region of the furnace wall where the combustion device is attached; and a second temperature detection unit that detects a second temperature in an upper region of the furnace wall where the combustion device is not attached and which is located above the lower region, and the control unit controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection unit and the second temperature detected by the second temperature detection unit.

2. The boiler system according to claim 1, wherein the control unit estimates a fuel ratio of the solid fuel based on the temperature difference and controls the boiler based on the fuel ratio.

3. The boiler system according to claim 2, wherein the boiler comprises a superheater having a superheater spray valve, and the control unit controls the operation of the superheater spray valve based on the fuel ratio.

4. A boiler system as described in any one of claims 1 to 3, wherein in the lower region of the furnace wall, the heat transfer tubes are formed in a spiral shape so as to extend in a direction inclined relative to the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed so as to extend along the vertical direction.

5. A boiler system as described in any one of claims 1 to 3, wherein in the lower region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction.

6. A method for controlling a boiler, wherein the boiler comprises: a furnace composed of a furnace wall having heat transfer tubes through which a fluid flows; a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace; a first temperature detection step for detecting a first temperature in a lower region of the furnace wall where the combustion device is attached; a second temperature detection step for detecting a second temperature in an upper region of the furnace wall where the combustion device is not attached and which is located above the lower region; and a control step for controlling the boiler based on the temperature difference between the first temperature detected by the first temperature detection step and the second temperature detected by the second temperature detection step.

7. The boiler control method according to claim 6, wherein the control step estimates a fuel ratio of the solid fuel based on the temperature difference, and controls the boiler based on the fuel ratio.

8. The boiler control method according to claim 7, wherein the boiler is provided with a superheater having a superheater spray valve, and the control step controls the operation of the superheater spray valve based on the fuel ratio.

9. A boiler control method as described in any one of claims 6 to 8, wherein in the lower region of the furnace wall, the heat transfer tubes are formed in a spiral shape so as to extend in a direction inclined relative to the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed so as to extend along the vertical direction.

10. A boiler control method as described in any one of claims 6 to 8, wherein in the lower region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction, and in the upper region of the furnace wall, the heat transfer tubes are formed to extend along the vertical direction.

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