Boiler systems and boiler control methods

Abstract

The objective of this invention is to allow for appropriate boiler control in response to changes in the properties of the solid fuel supplied to the combustion device, without requiring operator intervention. A means to solve this objective is to provide a boiler system comprising a boiler and a control unit for controlling the boiler. The boiler includes: a furnace (11) constructed by a furnace wall (101) having heat transfer tubes with fluid flow inside; a combustion device that injects solid fuel and combustion air into the furnace (11) to generate combustion gases; a first temperature detection unit that detects a first temperature in a lower region (101A) of the furnace wall (101) where the combustion device is installed; and a second temperature detection unit that detects a second temperature in an upper region (101B) of the furnace wall (101) where no combustion device is installed and located above the lower region (101A). 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.

Description

[Technical Field]

[0001] This invention relates to a boiler system and a boiler control method. [Previous Technology]

[0002] Coal-fired boilers that can switch between different types of coal are well-known (see, for example, Patent Document 1). Patent Document 1 discloses that in a coal-fired boiler that can switch between different types of coal, changes in the operating data of the coal mill are detected to determine the switching of coal type in the coal bunker, and the boiler control mechanism is set to the setting of the switched coal type. Furthermore, Patent Document 1 discloses detecting changes in combustion data such as boiler heat, boiler temperature distribution, and boiler efficiency to determine the coal type switching of the coal bunker with the shortest remaining coal consumption time at that point in time. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2007-315636 [Summary of the Invention]

[0004] [The problem the invention aims to solve]

[0005] While Patent Document 1 can detect changes in the operating data and combustion data of the coal mill to determine whether there is a change in the coal type in the coal bunker, the boiler control mechanism cannot be directly set based on the detection results of changes in the operating data and combustion data of the coal mill. The coal-fired boiler in Patent Document 1 has a storage means for storing property data such as calorific value and mass of coal types, and the property data of the switched coal type can be changed by the operator inputting the pre-switched coal type number.

[0006] That is, in Patent Document 1, although the timing of coal type switching can be detected from changes in the operating data and combustion data of the coal mill, the operator of the coal-fired boiler needs to pre-select the type of coal after switching or set the boiler control mechanism for that type. Therefore, in Patent Document 1, the operator needs to pre-identify the type of coal to be switched in the coal bunker and input the coal type number as the setting for the boiler control mechanism.

[0007] This invention was developed in view of the following situation, and its object is to provide a boiler system and boiler control method that can appropriately control the boiler in response to changes in the properties of the solid fuel supplied to the combustion device without operator intervention. [Technical Means for Solving the Problem]

[0008] One embodiment of the boiler system of the present invention comprises a boiler and a control unit for controlling the boiler. The boiler comprises: a furnace, which is constructed by a furnace wall having heat transfer tubes with fluid flow inside; a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gases; a first temperature detection unit that detects a first temperature in the furnace wall below where the combustion device is installed; and a second temperature detection unit that detects a second temperature in the furnace wall above where the combustion device is not installed and is located above the lower region. 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.

[0009] In one embodiment of the boiler control method of the present invention, the boiler comprises: a furnace, which is constructed by a furnace wall having heat transfer tubes having fluid flow inside; a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gases; a first temperature detection process that detects a first temperature in a region below the furnace wall where the combustion device is installed; and a second temperature detection process that detects 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; and a control process that controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process. [Effects of the Invention]

[0010] According to the present invention, a boiler system and boiler control method can be provided that do not require operator intervention even when the properties of the solid fuel supplied to the combustion device change, and can appropriately control the boiler in response to changes in the properties of the solid fuel.

Implementation Method

[0012] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to this embodiment; furthermore, when there are multiple embodiments, it includes combinations of the various embodiments. In the following description, "upper" and "above" refer to the upper part of the vertical direction, and "lower" and "below" refer to the lower part of the vertical direction. The vertical direction is not precise and includes errors.

[0013] Figure 1 shows a boiler system 100 equipped with a boiler 10 using pulverized solid fuel as the main fuel according to this embodiment. The boiler system 100 includes the boiler 10 and a control unit 50 for controlling the boiler 10. The boiler 10 of this embodiment is a boiler that generates superheated steam by burning pulverized solid fuel using a combustion device and exchanging the heat generated by the combustion with water supply and steam. Biomass fuel, coal, etc. are used as solid fuels.

[0014] The boiler 10 includes a furnace 11, a combustion device 20, and a combustion gas passage 12. The furnace 11 is a hollow, quadrangular cylinder arranged vertically. The furnace 11 is formed by a furnace wall 101 that forms the inner wall surface. The furnace wall 101 is composed of a plurality of heat transfer tubes in which fluid (water, steam) flows, and fins connecting the heat transfer tubes to each other. The furnace wall 101 exchanges and recovers the heat generated by the combustion of the pulverized fuel with the water or steam flowing inside the heat transfer tubes. The heat transfer tubes suppress the temperature rise of the furnace wall 101.

[0015] The combustion device 20 is a device for injecting solid fuel and combustion air into the furnace 11 to generate combustion gases. The combustion device 20 is located in the lower region 101A of the furnace 11. In this embodiment, the combustion device 20 has a plurality of blowtorches 21A, 21B, 21C, 21D, 21E, and 21F mounted on the furnace wall 101 (in the following description, only "blowtorch 21" will be referred to without distinguishing these blowtorches).

[0016] The blowtorches 21 are arranged in multiple layers along the furnace wall 101 at equal intervals in the furnace width direction (for example, arranged opposite each other in the furnace width direction on opposite furnace walls 101 in a manner that enables opposing combustion). The shape of the furnace, the number of blowtorch layers, the number of blowtorches in a layer, the arrangement of the blowtorches, etc., are not limited to this embodiment.

[0017] Blowtorches 21A, 21B, 21C, 21D, 21E, and 21F are connected to a plurality of grinders (crushers) 31A, 31B, 31C, 31D, 31E, and 31F (in the following description, these grinders are referred to as "grinders 31" without distinguishing them) via a plurality of micro-powder fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F respectively.

[0018] The grinder 31 is, for example, a vertical roller grinder consisting of an internally driven rotating support for a crushing table (not shown), and a plurality of crushing rollers (not shown) rotatably supported above the crushing table in conjunction with its rotation. The solid fuel that is crushed by the cooperation of the crushing rollers and the crushing table is transported to a classifier (not shown) provided in the grinder 31 by primary air (transportation gas, oxidizing gas) supplied to the grinder 31.

[0019] In the classifier, the fuel is classified into fine powder fuel with a particle size smaller than that suitable for combustion in the blowtorch 21 and coarse powder fuel with a larger particle size. The fine powder fuel is supplied to the blowtorch 21 along with primary air through the fine powder fuel supply pipe 22 via the classifier. The coarse powder fuel that does not pass through the classifier is left inside the grinder 31 by its own weight and is further ground on the crushing table.

[0020] Outside the furnace 11 where the blowtorch 21 is installed, a bellows (gas storage device) 23 is provided, and one end of an air duct (air conduit) 24 is connected to the bellows 23. At the other end of the air duct 24, a forced draft fan (FDF) 32 is connected. The air supplied from the forced draft fan 32 is heated in the air preheater 42 located in the air duct 24, and then supplied to the blowtorch 21 as secondary air (combustion air, oxidizing gas) via the bellows 23, and then introduced into the interior of the furnace 11.

[0021] The combustion gas passage 12 is connected to the upper part of the furnace 11 in the vertical direction. In the combustion gas passage 12, as heat exchangers for recovering heat from the combustion gases, there are superheaters 102A, 102B, and 102C (hereinafter referred to as "superheater 102" unless otherwise distinguished), reheaters 103A and 103B (hereinafter referred to as "reheater 103" unless otherwise distinguished), and an economizer 104. Heat exchange occurs between the combustion gases generated in the furnace 11 and the supply water, steam, etc., flowing inside each heat exchanger. Furthermore, the configuration and shape of each heat exchanger are not limited to the form shown in Figure 1.

[0022] Downstream of the combustion gas passage 12, a flue 13 is connected to discharge the combustion gas that is heat-recovered in the heat exchanger. An air preheater (air heater) 42 is provided between the flue 13 and the air duct 24, where heat exchange occurs between the air flowing in the air duct 24 and the combustion gas flowing in the flue 13, heating the primary air supplied to the grinder 31 and the secondary air supplied to the blowtorch 21, thereby further recovering heat from the combustion gas after heat exchange with water or steam.

[0023] Alternatively, a denitrification device 43 may be installed in the flue 13, upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent that reduces nitrogen oxides such as ammonia and urea water to the combustion gas flowing in the flue 13. Through the catalytic action of the denitrification catalyst installed in the denitrification device 43, the reaction between nitrogen oxides (NOx) in the combustion gas to which the reducing agent has been supplied is promoted and the reducing agent, thereby removing or reducing nitrogen oxides in the combustion gas.

[0024] A gas duct 41 is connected downstream of the air preheater 42 in the flue 13. The gas duct 41 is equipped with an environmental device such as a dust collection device 44 (e.g., an electrostatic precipitator to remove ash from the combustion gases) and a desulfurization device 46 (e.g., a desulfurization device to remove sulfur oxides), as well as an induced draft fan 45 for guiding exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to the chimney 47, where the combustion gases treated by the environmental devices are discharged as exhaust gas outside the system.

[0025] In boiler 10, during the combustion of pulverized fuel, a plurality of grinding mills 31 are driven to pulverize the solid fuel. Pulverized fuel classified by a classifier and primary air are supplied to blowtorch 21 via pulverized fuel supply pipe 22. In addition, secondary air, which has been heated by air preheater 42, is supplied to blowtorch 21 from air duct 24 via air box 23. Blowerch 21 blows the pulverized fuel-primary air mixture into furnace 11 and also blows secondary air into furnace 11.

[0026] The micro-powder fuel mixture blown into the furnace 11 ignites and reacts with secondary air to form a flame. The flame forms in the lower region of the furnace 11, and the high-temperature combustion gases rise within the furnace 11 and flow into the combustion gas passage 12. Furthermore, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but it can be an oxygen-rich gas or conversely, a gas with a lower oxygen content. By adjusting the ratio of oxygen to the amount of fuel supplied to an appropriate range, stable combustion is achieved in the furnace 11.

[0027] In addition, above the burner 21 in the furnace 11, there are a plurality of additional ventilation ports (AA ports) 25 for supplying additional air for combustion into the furnace 11. At the end of the additional ventilation port 25, there are additional air ducts (AA ducts) branching from the air duct 24, which can supply a portion of the air supplied from the push ventilation fan 32 as additional air for combustion to the additional ventilation port 25 via the additional air ducts 26.

[0028] In region A (the region corresponding to the height range of the bellows 23) inside the furnace 11 shown in Figure 1, a flame is formed by the combustion of a mixture of primary air and powdered fuel and secondary air. Here, by setting the air ratio in region A to less than 1, specifically, the amount of air supplied to the blowtorch 21 (the total amount of primary and secondary air) is set to be less than the theoretical amount of air supplied to the blowtorch 21 for the amount of fuel. As a result, regions A and B (the region between the uppermost part of the blowtorch 21 and the lowermost part of the auxiliary ventilation port 25) inside the furnace 11 become a reducing environment, and the nitrogen oxides (NOx) produced by combustion are reduced inside the furnace 11. Then, in region C (the region above the lowermost part of the auxiliary ventilation port 25), the combustion gas from which the nitrogen oxides (NOx) are reduced is supplied with additional air for combustion from the auxiliary ventilation port 25 to complete the combustion. However, based on the reduction effect of regions A and B, the amount of nitrogen oxides (NOx) produced is reduced.

[0029] The combustion gas flowing into the combustion gas passage 12 exchanges heat with water or steam through the superheater 102, reheater 103, and economizer 104 located inside the combustion gas passage 12, and is then discharged to the flue 13. Nitrogen oxides are removed by the denitrification device 43, and after heat exchange with primary and secondary air in the air preheater 42, it is further discharged to the gas duct 41. Ash and other pollutants are removed by the dust collection device 44, and sulfur oxides are removed by the desulfurization device 46 before being discharged outside the system through the chimney 47. Furthermore, the arrangement of the heat exchangers in the combustion gas passage 12 and the devices in the flue 13 to the gas duct 41 does not necessarily have to be in the order described above for the flow of combustion gas.

[0030] The control unit 50 is a device used to control various parts of the boiler 10. The control unit 50 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a storage medium that can be read by a computer. Furthermore, the series of processes used to implement various functions are, for example, stored in the form of a program on a storage medium, etc. The CPU reads this program into RAM, etc., and performs information processing and calculation to realize various functions.

[0031] Furthermore, the program may be provided in the form of being pre-downloaded to ROM and other storage media, provided while stored on a computer-readable storage medium, or transmitted via wired or wireless communication means. Computer-readable storage media refers to magnetic disks, optical disks, CD-ROMs, DVD-ROMs, semiconductor memory, etc.

[0032] Next, referring to Figures 2 to 4, the first temperature detection unit 60 and the second temperature detection unit 70 for detecting the temperature of the furnace wall 101 will be described. Figure 2 is a perspective view of a furnace 11 showing an embodiment of the present invention. Figure 3 is a cross-sectional view of the lower region 101A of the furnace wall 101 shown in Figure 2, indicated by arrow CC. Figure 4 is a cross-sectional view of the upper region 101B of the furnace wall 101 shown in Figure 2, indicated by arrow DD. Furthermore, the furnace 11 and furnace wall 101 shown in Figures 2 to 4 are examples, and the shape of the furnace 11 and furnace wall 101 can be modified in various ways.

[0033] As shown in Figures 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 for the blowtorches 21D, 21E, and 21F on which the combustion devices 20 are installed; a rear wall 101b for the blowtorches 21A, 21B, and 21C on which the combustion devices 20 are installed; a right side wall 101c that forms the right side of the furnace 11; and a left side wall 101d that forms the left side of the furnace 11.

[0034] In Figure 2, the symbols 21Aa, 21Ba, 21Ca, 21Da, 21Ea, and 21Fa respectively indicate the positions where the blowtorches 21A, 21B, 21C, 21D, 21E, and 21F are installed.

[0035] As shown in Figure 2, in the lower region 101A of the furnace wall 101, a heat transfer tube 101C is formed extending in a direction inclined relative to the vertical direction VD. As the heat transfer tube 101C moves along the vertical direction VD, it forms a spiral shape that rotates in the order of front wall 101a, right side wall 101c, rear wall 101b, and left side wall 101d. Alternatively, the heat transfer tube 101C may be formed on the front wall 101a, right side wall 101c, rear wall 101b, and left side wall 101d respectively, extending along the vertical direction VD.

[0036] Furthermore, as shown in FIG2, in the upper region 101B of the furnace wall 101, the heat transfer tube 101C is formed in such a way that it extends along the vertical direction VD. The heat transfer tube 101C in the lower region 101A and the heat transfer tube 101C in the upper region 101B are connected at the connection point between the lower region 101A and the upper region 101B in such a way that fluid (water, steam) can flow continuously between them.

[0037] As shown in FIG3, the boiler 10 of this embodiment includes a first temperature detection unit 60, which detects the first temperature T1 of the region 101A below the combustion device 20 in the furnace wall 101. The first temperature detection unit 60 is installed in the region 101A below the blowtorches 21A, 21B, 21C, 21D, 21E, and 21F of the combustion device 20 in the furnace wall 101 to detect the first temperature T1 [°C] of the region 101A below.

[0038] As shown in FIG3, 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 a first temperature T1 [°C] as, for example, the average value of the temperatures output from the first temperature detection sensors 60a to 60t.

[0039] In addition, the first temperature detection unit 60 can also detect the first temperature T1 by a predetermined calculation method based on the highest temperature among the temperatures output from the first temperature detection sensors 60a to 60t, the median value of the standard deviation of the temperatures output from the first temperature detection sensors 60a to 60t, etc.

[0040] As shown in FIG4, the boiler 10 of this embodiment includes a second temperature detection unit 70, which detects a second temperature T2 in the upper region 101B of the furnace wall 101 where no combustion device 20 is installed and which is located above the lower region 101A. The second temperature detection unit 70 is installed in the upper region 101B of the furnace wall 101 above the blowtorches 21A, 21B, 21C, 21D, 21E, and 21F where no combustion device 20 is installed, to detect the second temperature T2 [°C] of the upper region 101B.

[0041] As shown in FIG3, 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 a second temperature T2 [°C] as, for example, the average value of the temperatures output from the second temperature detection sensors 70a to 70t.

[0042] In addition, the second temperature detection unit 70 can also detect the second temperature T2 by a predetermined calculation method based on the highest temperature among the temperatures output from the second temperature detection sensors 70a to 70t, the median value of the standard deviation of the temperatures output from the second temperature detection sensors 70a to 70t, etc.

[0043] Next, referring to FIG5, a control method for the boiler 10 of this embodiment will be described. FIG5 is a flowchart showing a control method for the boiler 10 of an embodiment of the present invention. The control unit 50 executes a control program to perform various processes as shown in FIG5. The processes shown in FIG5 are the processes performed by the control unit 50 during the operation of the boiler 10.

[0044] In step S101, the control unit 50 obtains the first temperature T1 of the region 101A below the furnace wall 101 detected by the first temperature detection unit 60. The first temperature detection unit 60, in response to receiving a control command from the control unit 50 regarding the detected first temperature T1, transmits the first temperature T1 of the region 101A below the furnace wall 101 to the control unit 50.

[0045] In step S102, the control unit 50 obtains the second temperature T2 of the region 101B above the furnace wall 101 detected by the second temperature detection unit 70. In response to the control command received from the control unit 50 regarding the detected second temperature T2, the second temperature detection unit 70 transmits the second temperature T2 of the region 101B above the furnace wall 101 to the control unit 50.

[0046] In step S103, the control unit 50 determines whether the temperature difference between the second temperature T2 and the first temperature T1 is higher than the predetermined temperature Ta. If it is yes (YES), the process proceeds to step S104 for processing. If it is no (NO), the process proceeds to step S105 for processing.

[0047] In step S104, the control unit 50 estimates that the type of solid fuel is low fuel ratio coal based on the fact that the temperature difference between the second temperature T2 and the first temperature T1 is higher than the predetermined temperature Ta.

[0048] In step S105, the control unit 50 determines whether the temperature difference between the second temperature T2 and the first temperature T1 is lower than the predetermined temperature Tb. If it is yes (YES), the process proceeds to step S106 for processing. If it is no (NO), the process proceeds to step S107 for processing.

[0049] In this embodiment, the temperature difference between a first temperature T1 and a second temperature T2 when multiple types of solid fuels are burned is obtained in advance, so that the type of solid fuel corresponds to the pre-obtained temperature difference between the first temperature T1 and the second temperature T2, and then a predetermined temperature Ta and a predetermined temperature Tb are set. For example, according to the order of the fuel ratio of solid fuels, the temperature difference between the first temperature T1 and the second temperature T2 when burning three types of solid fuels with high fuel ratio, medium fuel ratio, and low fuel ratio is obtained in advance.

[0050] Furthermore, the temperature difference between the first temperature T1 and the second temperature T2 when burning solid fuel with a high fuel ratio and the temperature difference between the first temperature T1 and the second temperature T2 when burning solid fuel with a medium fuel ratio are set as a predetermined temperature Tb. Additionally, the temperature difference between the first temperature T1 and the second temperature T2 when burning solid fuel with a medium fuel ratio and the temperature difference between the first temperature T1 and the second temperature T2 when burning solid fuel with a low fuel ratio are set as a predetermined temperature Ta.

[0051] In step S106, the control unit 50 estimates that the solid fuel is high fuel ratio coal based on the fact that the temperature difference between the second temperature T2 and the first temperature T1 is lower than the predetermined temperature Tb.

[0052] In step S107, the control unit 50 estimates that the type of solid fuel is medium fuel ratio coal based on the fact that the temperature difference between the second temperature T2 and the first temperature T1 is lower than the predetermined temperature Ta and higher than the predetermined temperature Tb.

[0053] In step S108, the control unit 50 estimates the solid fuel ratio 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 then sets the 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 according to the set control parameters.

[0054] Here, the control parameters of boiler 10 refer to various parameters that affect the operating characteristics of boiler 10, such as the flow rate setting of the superheater spray valve of superheater 102. Additionally, the control parameters of boiler 10 refer to, for example, the spray flow rate used to control the superheater spray valve to achieve the correct temperature for the main steam temperature. The control unit 50 estimates the solid fuel ratio 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 then controls the operation of the superheater spray valve based on the fuel ratio.

[0055] In addition to the flow setting of the superheater spray valve, there are parameters used to stabilize the boiler operation according to the load (such as the set values ​​of the outlet temperature and inlet temperature of each heat transfer tube). These control parameters are switched according to the type of solid fuel.

[0056] Furthermore, in the flowchart of FIG5, it is shown that the control unit 50 estimates the solid fuel ratio 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 then sets the control parameters for controlling the boiler 10 based on the fuel ratio. However, other states are also possible. For example, the control unit 50 may also 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.

[0057] For example, when controlling the flow rate of the superheater spray valve of the superheater 102, which is a control parameter, the spray flow rate is determined based on the temperature difference between the first temperature T1 and the second temperature T2, corresponding to a pre-determined main steam temperature. Furthermore, for other control parameters (such as the outlet and inlet temperatures of each heat transfer tube), the setpoints of the control parameters are also pre-determined based on the temperature difference between the first temperature T1 and the second temperature T2.

[0058] The boiler system 100 of this embodiment, as described above, achieves the following functions and effects. In the boiler system of this embodiment, the first temperature of the lower region of the furnace wall where the combustion device is installed is detected by the first temperature detection unit, and the second temperature of the upper region of the furnace wall where no combustion device is installed and which is located above the lower region is detected by the second temperature detection unit. The inventors have obtained the following new insight: the larger the temperature difference between the second temperature and the first temperature, the lower the fuel ratio of the solid fuel becomes; conversely, the smaller the temperature difference between the second temperature and the first temperature, the higher the fuel ratio of the solid fuel becomes.

[0059] 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. Since the temperature difference corresponds to the fuel ratio of solid fuel, no operator intervention is required, and the boiler 10 can be appropriately controlled according to changes in the properties of solid fuel.

[0060] In addition, according to the boiler system 100 of this embodiment, the fuel ratio of solid fuel is 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 is appropriately controlled based on the fuel ratio.

[0061] In addition, 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.

[0062] Furthermore, according to the boiler system 100 of this embodiment, the boiler 10 can be correctly controlled in response to changes in the properties of solid fuel by the temperature difference between the first temperature T1 of the lower region 101A of the furnace wall 101 and the second temperature T2 of the upper region 101B of the furnace wall 101 formed by the heat transfer tube extending in the vertical direction VD.

[0063] Furthermore, according to the boiler system 100 of this embodiment, the boiler 10 can be correctly controlled in response to changes in the properties of solid fuel by the temperature difference between the first temperature T1 of the lower region 101A of the furnace wall 101 formed along the vertical direction by the heat transfer tube and the second temperature T2 of the upper region 101B of the furnace wall 101 formed by the heat transfer tube extending along the vertical direction VD.

[0064] The boiler system and boiler control method described in the above embodiments are as follows.

[0065] The boiler system of the first aspect of the present invention includes a boiler (10) and a control unit (50) for controlling the boiler. The boiler includes: a furnace (11) which is constructed by a furnace wall (101) having heat transfer tubes with fluid flow inside; a combustion device (20) which injects solid fuel and combustion air into the furnace to generate combustion gas; a first temperature detection unit (60) which detects a first temperature (T1) in the lower region (101A) of the furnace wall where the combustion device is installed; and a second temperature detection unit (70) which detects a second temperature (T2) in the upper region (101B) of the furnace wall where the combustion device is not installed and is located above the lower region. 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.

[0066] According to the boiler system of the first embodiment of the present invention, the first temperature of the lower region of the furnace wall where the combustion device is installed is detected by the first temperature detection unit, and the second temperature of the 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 obtained the following new insight: the larger the temperature difference between the second temperature and the first temperature, the lower the fuel ratio of solid fuel becomes; the smaller the temperature difference between the second temperature and the first temperature, the higher the fuel ratio of solid fuel becomes.

[0067] According to the boiler system of the first embodiment of the present invention, the boiler is controlled 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. Since the temperature difference corresponds to the fuel ratio of solid fuel, no operator intervention is required, and the boiler can be appropriately controlled according to changes in the properties of solid fuel.

[0068] The boiler system of the second embodiment of the present invention, as in the first embodiment, further includes the following structure. That is, the aforementioned control unit estimates the fuel ratio of the aforementioned solid fuel based on the aforementioned temperature difference, and then controls the aforementioned boiler based on the aforementioned fuel ratio. In the boiler system of the second embodiment of the present invention, the fuel ratio of the solid fuel is 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 then the boiler is appropriately controlled based on the fuel ratio.

[0069] The boiler system of the third embodiment of the present invention, as in the second embodiment, further includes the following structure. That is, the boiler includes a superheater with 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 of the third embodiment of the present invention, the operation of the superheater spray valve is controlled based on a fuel ratio estimated from the temperature difference between a first temperature detected by a first temperature detection unit and a second temperature detected by a second temperature detection unit. This allows for appropriate control of the boiler in response to changes in the properties of the solid fuel.

[0070] The boiler system of the fourth embodiment of the present invention, as in any of the first to third embodiments, further comprises the following structure: In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a spiral shape extending in a direction inclined to the vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend along the aforementioned vertical direction. According to the boiler system of the fourth embodiment of the present invention, the boiler can be correctly controlled in response to changes in the properties of the solid fuel based on the temperature difference between the first temperature of the lower region of the furnace wall where the heat transfer tube is formed in a spiral shape and the second temperature of the upper region of the furnace wall where the heat transfer tube extends along the vertical direction.

[0071] The boiler system of the fifth embodiment of the present invention, as in any of the first to third embodiments, further comprises the following structure: That is, in the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a manner extending along a vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a manner extending along the aforementioned vertical direction. According to the boiler system of the fifth embodiment of the present invention, based on the temperature difference between the first temperature of the lower region of the furnace wall where the heat transfer tube is formed in a straight direction and the second temperature of the upper region of the furnace wall where the heat transfer tube is formed in a manner extending along a vertical direction, the boiler can be correctly controlled in response to changes in the properties of the solid fuel.

[0072] In the boiler control method of the sixth aspect of the present invention, the boiler includes: a furnace, which is constructed by a furnace wall having heat transfer tubes having fluid flow inside; and a combustion device that generates combustion gas by injecting solid fuel and combustion air into the furnace. The control method includes: a first temperature detection process that detects a first temperature in the furnace wall below where the combustion device is installed; a second temperature detection process that detects a second temperature in the furnace wall above where the combustion device is not installed and is located above the lower region; and a control process that controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process.

[0073] According to the boiler control method of the sixth embodiment of the present invention, the first temperature of the lower region of the furnace wall where the combustion device is installed is detected by the first temperature detection process, and the second temperature of the 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 process. The inventors have obtained the following new insight: the larger the temperature difference between the second temperature and the first temperature, the lower the fuel ratio of solid fuel becomes; the smaller the temperature difference between the second temperature and the first temperature, the higher the fuel ratio of solid fuel becomes.

[0074] According to the boiler control method of the sixth state of the present invention, the boiler is controlled based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process. Since the temperature difference corresponds to the fuel ratio of solid fuel, no operator intervention is required, and the boiler can be appropriately controlled according to changes in the properties of solid fuel.

[0075] The boiler control method of the seventh embodiment of the present invention, as in the sixth embodiment, further includes the following structure. That is, the aforementioned control process estimates the fuel ratio of the aforementioned solid fuel based on the aforementioned temperature difference, and then controls the aforementioned boiler based on the aforementioned fuel ratio. According to the boiler control method of the seventh embodiment of the present invention, the fuel ratio of the solid fuel is estimated based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process, and then the boiler is appropriately controlled based on the fuel ratio.

[0076] The boiler control method of the eighth embodiment of the present invention, as in the seventh embodiment, further includes the following structure. That is, the aforementioned boiler includes a superheater, which has a superheater spray valve, and the aforementioned control process controls the operation of the aforementioned superheater spray valve based on the aforementioned fuel ratio. According to the boiler control method of the eighth embodiment of the present invention, the operation of the superheater spray valve is controlled based on the fuel ratio estimated based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process. In this way, the boiler can be appropriately controlled according to changes in the properties of the solid fuel.

[0077] The boiler control method of the ninth embodiment of the present invention, as in any one of the sixth to eighth embodiments, further comprises the following structure: In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a spiral shape extending in a direction inclined to the vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend along the aforementioned vertical direction. According to the boiler control method of the ninth embodiment of the present invention, based on the temperature difference between the first temperature of the lower region of the furnace wall where the heat transfer tube is formed in a spiral shape and the second temperature of the upper region of the furnace wall where the heat transfer tube extends along the vertical direction, the boiler can be correctly controlled in response to changes in the properties of the solid fuel.

[0078] The boiler control method of the tenth embodiment of the present invention, such as any one of the sixth to eighth embodiments, further includes the following structure: That is, in the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a manner extending along the vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a manner extending along the aforementioned vertical direction. According to the boiler control method of the tenth embodiment of the present invention, based on the temperature difference between the first temperature of the lower region of the furnace wall where the heat transfer tube is formed to extend along the vertical direction and the second temperature of the upper region of the furnace wall where the heat transfer tube is formed to extend along the vertical direction, the boiler can be correctly controlled in response to changes in the properties of the solid fuel. [Simplified Explanation of the Diagram]

[0011] [Figure 1] is a schematic diagram showing the configuration of a boiler system according to an embodiment of the present invention. [Figure 2] is a perspective view showing a furnace according to an embodiment of the present invention. [Figure 3] is a cross-sectional view of the lower region of the furnace wall shown in Figure 2 (arrow CC). [Figure 4] is a cross-sectional view of the upper region of the furnace wall shown in Figure 2 (arrow DD). [Figure 5] is a flowchart showing a boiler control method according to an embodiment of the present invention.

Claims

1. A boiler system comprising: a boiler; and a control unit that controls the boiler, the boiler comprising: a furnace wall formed by heat transfer tubes having fluid flow inside; a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gases; a first temperature detection unit that detects a first temperature in a region below the furnace wall where the combustion device is installed; 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 installed and is located above the lower region; 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; 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.

2. The boiler system as described in claim 1, wherein, The aforementioned boiler includes: a superheater having a superheater spray valve, wherein the aforementioned control unit controls the operation of the aforementioned superheater spray valve according to the aforementioned fuel ratio.

3. The boiler system as described in claim 1 or 2, wherein, In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a spiral shape extending in a direction inclined to the vertical direction. In the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend along the aforementioned vertical direction.

4. The boiler system as described in claim 1 or 2, wherein, In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend in a vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend in the aforementioned vertical direction.

5. A method for controlling a boiler, the boiler comprising: a furnace, which is formed by a furnace wall having heat transfer tubes with fluid flow inside; a combustion device that injects solid fuel and combustion air into the furnace to generate combustion gases, the control method comprising: a first temperature detection process that detects a first temperature in a region below the furnace wall where the combustion device is installed; a second temperature detection process that detects 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; and a control process that controls the boiler based on the temperature difference between the first temperature detected by the first temperature detection process and the second temperature detected by the second temperature detection process, wherein the control process estimates the fuel ratio of the solid fuel based on the temperature difference and then controls the boiler based on the fuel ratio.

6. The boiler control method as described in claim 5, wherein, The aforementioned boiler also includes: a superheater having a superheater spray valve, wherein the aforementioned control process controls the operation of the aforementioned superheater spray valve according to the aforementioned fuel ratio.

7. The boiler control method as described in claim 5 or 6, wherein, In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed in a spiral shape extending in a direction inclined to the vertical direction. In the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend along the aforementioned vertical direction.

8. The boiler control method as described in claim 5 or 6, wherein, In the aforementioned lower region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend in a vertical direction, and in the aforementioned upper region of the aforementioned furnace wall, the aforementioned heat transfer tube is formed to extend in the aforementioned vertical direction.

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