Boiler

Abstract

To prevent a situation in which soot removal is difficult.SOLUTION: A boiler 1 comprises a can body 2 comprising a water pipe 11, a burner 3 connected to the can body 2, a blower 4 for sending air to the burner 3, a furnace-pressure sensor 9 for detecting the furnace pressure value showing the inner pressure of the can body 2, and a controller 10. The controller 10 comprises a reference value memory unit 21 for memorizing a reference value showing the pressure in the can body 2 at a time when the flow-rates of fuel and air being sent to the burner 3 are adjusted to suitable ones, a relative threshold setting unit 22 for setting a first relative threshold obtained by multiplying the reference value by a first real number greater than 1, an absolute threshold memory unit 23 for memorizing a first absolute threshold, i.e., the upper limit relating to the furnace pressure value, and a determination unit 24 for determining if the furnace pressure has exceeded at least one of the first relative threshold and the first absolute threshold, or not.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a boiler. [Background technology]

[0002] In the technical field related to boilers, a boiler apparatus as disclosed in Patent Document 1 is known. In Patent Document 1, fuel mixed with air is supplied to a burner. The air is supplied to the burner from a blower through an air passage. The air used for burning the fuel in the burner passes through the inside of the boiler body and is then discharged from a flue as exhaust gas.

[0003] Fuel is supplied to the burner with the air ratio, which is the ratio of air to fuel, adjusted to an appropriate value. By supplying fuel with an air ratio adjusted to an appropriate value to the burner, the fuel is burned appropriately in the burner.

[0004] The combustion of fuel in the burner can generate soot. The generated soot can accumulate or adhere to the flow path downstream of the burner. If the flow path becomes narrower due to the presence of soot, the air flow from the blower to the burner becomes poor, and the flow rate of air sent from the blower to the burner decreases. If the flow rate of air sent to the burner decreases below the appropriate amount, the air ratio decreases. In other words, if the flow rate of air sent to the burner decreases below the appropriate amount, the air ratio becomes an inappropriate value.

[0005] When the air ratio becomes an inappropriate value, an adjustment process is performed to increase the output of the blower, thereby increasing the flow rate of air sent from the blower to the burner and returning the air ratio to an appropriate value. Even if a cleaning operation to remove soot from the flow path is not performed, the air ratio is returned to an appropriate value by performing an adjustment process to increase the output of the blower. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-143914 A Summary of the Invention [Problem to be solved by the invention]

[0007] The adjustment process is performed, for example, during regular inspection of the boiler. The adjustment process is performed manually by an inspector. By performing the adjustment process, a reference value indicating the pressure inside the boiler body when the air ratio is adjusted to an appropriate value is updated. If the adjustment process is performed without performing a cleaning operation, the reference value after the adjustment process will be higher than the reference value before the adjustment process, so the reference value increases each time it is updated. If the adjustment process is performed multiple times without performing a cleaning operation, the air ratio will be adjusted to an appropriate value, but the amount of soot present in the flow path will gradually increase, and it may eventually become difficult to remove the soot from the flow path. If it becomes difficult to remove the soot from the flow path, for example, a situation may arise where the boiler body needs to be replaced, and the cost required for replacement will be incurred.

[0008] The technology disclosed in this specification aims to prevent situations in which soot removal becomes difficult. [Means for solving the problem]

[0009] This specification discloses a boiler. The boiler includes a boiler body having a water tube, a burner connected to the boiler body, a blower for sending air to the burner, a furnace pressure sensor for detecting a furnace pressure value indicating the pressure inside the boiler body, and a controller. The controller includes a reference value storage unit for storing a reference value indicating the pressure inside the boiler body when the flow rates of fuel and air sent to the burner are adjusted to appropriate amounts, a relative threshold setting unit for setting a first relative threshold value obtained by multiplying the reference value by a first real number greater than 1, an absolute threshold storage unit for storing a first absolute threshold value that is an upper limit value related to the furnace pressure value, and a determination unit for determining whether the furnace pressure value exceeds at least one of the first relative threshold value and the first absolute threshold value. Effect of the Invention

[0010] According to the technology disclosed in this specification, it is possible to prevent situations in which it becomes difficult to remove soot. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a boiler according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing a boiler according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing the relationship between the combustion amount, the reference value, the first real number, the first relative threshold value, and the first absolute threshold value according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the combustion amount, the reference value, the second real number, the second relative threshold value, and the second absolute threshold value according to the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a relationship between the first relative threshold value and the first absolute threshold value according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of a relationship between the second relative threshold value and the second absolute threshold value according to the embodiment. [Figure 7] FIG. 7 is a diagram for explaining the operation of the boiler according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating a schematic view of a part of a boiler according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiment. The components of the embodiments described below can be appropriately combined. In addition, some components may not be used.

[0013] [Boiler] 1 is a diagram illustrating a boiler 1 according to an embodiment of the present invention. The boiler 1 includes a boiler body 2, a burner 3, a blower 4, an air passage 5, a fuel supply passage 6, a flue 7, a duct 8, a furnace pressure sensor 9, and a controller 10.

[0014] The boiler body 2 has a water tube 11. The water tube 11 is disposed inside the boiler body 2. Water is supplied to the water tube 11. A plurality of water tubes 11 are provided. An upper portion of each of the plurality of water tubes 11 is connected to a steam header.

[0015] The burner 3 is connected to the boiler body 2. The burner 3 burns fuel mixed with air. The fuel is a gaseous fuel. The fuel is burned by a premix method. The fuel is burned in the burner 3, whereby the water tube 11 is heated. The water tube 11 is heated to generate steam.

[0016] The blower 4 sends air to the burner 3. The blower 4 is controlled by a controller 10. The blower 4 and the boiler body 2 are connected via an air passage 5. The air passage 5 distributes the air supplied to the burner 3. The blower 4 sends air to the burner 3 via the air passage 5. The air is supplied to the burner 3 via the air passage 5.

[0017] The fuel supply passage 6 distributes fuel to be supplied to the burner 3. The fuel supply passage 6 is connected to the air passage 5. Fuel is supplied to the burner 3 via the fuel supply passage 6 and the air passage 5. In the air passage 5, air from the blower 4 and fuel from the fuel supply passage 6 are mixed. The fuel and air mixed in the air passage 5 are supplied to the burner 3. In the burner 3, the fuel mixed with the air is combusted.

[0018] The flue 7 is connected to the boiler body 2. Exhaust gas discharged from the boiler body 2 flows through the flue 7. Air used for burning fuel in the burner 3 passes through the boiler body 2 and is then discharged from the flue 7 as exhaust gas.

[0019] An on-off valve 12 and a regulating valve 13 are disposed in the fuel supply passage 6. The on-off valve 12 opens and closes the fuel supply passage 6. The regulating valve 13 regulates the flow rate of fuel supplied to the burner 3. The regulating valve 13 is controlled by a controller 10. The regulating valve 13 is disposed downstream of the on-off valve 12.

[0020] The duct 8 is connected to both the air passage 5 and the can body 2. One end of the duct 8 is connected to the air passage 5. The other end of the duct 8 is connected to the can body 2.

[0021] The furnace pressure sensor 9 detects a furnace pressure value indicating the pressure inside the can body 2. The furnace pressure sensor 9 may adopt any configuration as long as it can detect the pressure inside the can body 2. It is only necessary that the decrease in the flow rate of air supplied to the burner 3 and the increase in the pressure inside the can body 2 can be determined based on the detection value of the furnace pressure sensor 9. The furnace pressure sensor 9 may be disposed inside the can body 2 and directly detect the pressure inside the can body 2. The furnace pressure sensor 9 may detect a gas pressure indicating the pressure of the fuel supply path 6. The furnace pressure sensor 9 may detect the discharge pressure of the blower 4 indicating the pressure at a position near the blower 4 in the air passage 5. The furnace pressure sensor 9 may detect the air passage pressure indicating the pressure at a position near the burner 3 in the air passage 5. The furnace pressure sensor 9 may detect the flow speed at the intake port of the blower 4. The furnace pressure sensor 9 may detect an inverter current value (power value) that controls the electric motor of the blower 4. For example, as disclosed in JP 2019-143914 A, when a first communication passage communicating with the air passage, a second communication passage communicating with the boiler body (boiler body), a first pressure reduction section arranged in the first communication passage, and a second pressure reduction section arranged in the second communication passage are provided, the furnace pressure sensor 9 may detect an intermediate pressure indicating the pressure difference between the first communication passage and the second communication passage.

[0022] In the embodiment, the furnace pressure sensor 9 is disposed in the duct 8. In the embodiment, the furnace pressure sensor 9 detects the pressure difference between the air blower 5 and the boiler body 2. The furnace pressure value detected by the furnace pressure sensor 9 is transmitted to the controller 10.

[0023] The controller 10 performs arithmetic processing. The controller 10 controls the boiler 1. The controller 10 includes a computer system. The controller 10 has a processor such as a CPU (Central Processing Unit), a main memory including a non-volatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory), a storage, and an interface including an input / output circuit. Each function of the controller is stored in the storage as a computer program. The processor reads the computer program from the storage and loads it into the main memory, and executes processing according to the computer program. The computer program may be distributed to the controller 10 via a network.

[0024] 2 is a block diagram showing the boiler 1 according to the embodiment. The boiler 1 includes a controller 10, a furnace pressure sensor 9, and an alarm device 14.

[0025] The controller 10 includes a reference value storage unit 21 , a relative threshold setting unit 22 , an absolute threshold storage unit 23 , a determination unit 24 , and a control unit 25 .

[0026] The reference value storage unit 21 stores a reference value related to the pressure inside the can body 2. The reference value refers to the pressure inside the can body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts. By adjusting the flow rates of fuel and air sent to the burner 3 to appropriate amounts, the air ratio, which is the ratio of air to fuel, is adjusted to an appropriate value. Therefore, the reference value may be considered to be the pressure inside the can body 2 when the air ratio of the fuel supplied from the air passage 5 to the burner 3 is adjusted to an appropriate value.

[0027] The relative threshold setting unit 22 sets a relative threshold related to a reference value. The relative threshold is a value obtained by multiplying the reference value by a real number greater than 1. The real number is a predetermined value. In the embodiment, the relative threshold setting unit 22 sets a first relative threshold obtained by multiplying the reference value by a first real number greater than 1, and a second relative threshold obtained by multiplying the reference value by a second real number greater than the first real number. Each of the first real number and the second real number is a predetermined value.

[0028] The absolute threshold storage unit 23 stores an absolute threshold that is an upper limit value related to the reactor pressure value. The absolute threshold value is a predetermined value. In the embodiment, the absolute threshold storage unit 23 stores a first absolute threshold that is an upper limit value related to the reactor pressure value, and a second absolute threshold value that is greater than the first absolute threshold value. Each of the first absolute threshold value and the second absolute threshold value is a predetermined value.

[0029] The determination unit 24 determines whether the reactor pressure value exceeds at least one of a relative threshold value and an absolute threshold value. The determination unit 24 determines whether the reactor pressure value exceeds at least one of a first relative threshold value and a first absolute threshold value. The determination unit 24 determines whether the reactor pressure value exceeds at least one of a second relative threshold value and a second absolute threshold value.

[0030] The control unit 25 outputs a control command based on the determination result to the determination unit 24. Based on the determination result of the determination unit 24, the control unit 25 controls the alarm device 14.

[0031] [Reference value] As described above, the reference value refers to the pressure inside the can body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts. The reference value refers to the pressure inside the can body 2 when the air ratio of the fuel supplied to the burner 3 from the air passage 5 is adjusted to an appropriate value. When the pressure inside the can body 2 is the reference value, the air ratio is determined to be an appropriate value. By supplying fuel with an air ratio adjusted to an appropriate value to the burner 3, the fuel is burned appropriately in the burner 3.

[0032] The combustion of fuel in the burner 3 may cause soot to be generated. The generated soot may remain or adhere to the flow path downstream of the burner 3. The flow path downstream of the burner 3 includes at least one of the inside of the can body 2 and the inside of the flue 7. The presence of soot may narrow the flow path downstream of the burner 3. If the presence of soot narrows the flow path downstream of the burner 3, the flow of air from the blower 4 to the burner 3 may become poor, and the flow rate of air sent from the blower 4 to the burner 3 may decrease. If the flow rate of air sent to the burner 3 decreases below an appropriate amount, the air ratio may decrease. In other words, if the flow rate of air sent to the burner 3 decreases below an appropriate amount, the air ratio may become an inappropriate value. If the air ratio becomes an inappropriate value, poor combustion may occur in the burner 3.

[0033] When the air ratio becomes inappropriate due to the generation of soot, an adjustment process is performed to increase the output of the blower 4, thereby increasing the flow rate of air sent from the blower 4 to the burner 3, and the air ratio is returned to the appropriate value. In addition, by performing a cleaning operation to remove soot from the flow path, the air ratio can be returned to the appropriate value even without performing an adjustment process.

[0034] When soot is not present in the flow path, the reference value is a low value. When the flow path is narrowed due to the presence of soot, causing the air ratio to decrease, an adjustment process is performed to increase the output of the blower 4, and the air ratio is returned to an appropriate value without performing a cleaning operation. When the output of the blower 4 is increased to increase the flow rate of air sent from the blower 4 to the burner 3, the pressure inside the boiler body 2 increases. Therefore, the reference value after the adjustment process is performed will be higher than the reference value before the adjustment process was performed.

[0035] After the adjustment process is performed, the reference value is stored in the reference value storage unit 21. For example, in a state where fuel having an air ratio adjusted to an appropriate value by the adjustment process is supplied to the burner 3, the pressure inside the boiler body 2 is detected by the furnace pressure sensor 9, thereby obtaining the reference value. The reference value obtained by the adjustment process is stored in the reference value storage unit 21.

[0036] The adjustment process updates the reference value stored in the reference value storage unit 21. If the adjustment process is performed without performing a cleaning operation, the reference value after the adjustment process will be higher than the reference value before the adjustment process, so the reference value increases each time it is updated.

[0037] If the adjustment process is performed multiple times without performing cleaning work, the air ratio will be adjusted to the appropriate value, but the amount of soot present in the flow path downstream of burner 3 will gradually increase, and it may eventually become difficult to remove the soot from the flow path.

[0038] [Relationship between combustion amount, reference value, actual number, relative threshold, and absolute threshold] FIG. 3 is a diagram showing the relationship between the combustion amount, the reference value, the first real number, the first relative threshold value, and the first absolute threshold value according to the embodiment.

[0039] In the embodiment, the combustion amount in the can body 2 is changed to a plurality of mutually different combustion amounts. In the embodiment, the combustion amount in the can body 2 is changed to a low combustion amount, a medium combustion amount, and a high combustion amount. The combustion amount [kW / h] refers to the amount of heat generated per unit time in the combustion chamber of the can body 2 in which the burner 3 is arranged. The high combustion amount is a combustion amount higher than the medium combustion amount. The medium combustion amount is a combustion amount higher than the low combustion amount. The high combustion amount is a combustion amount that can continuously exert the maximum capacity of the boiler 1 under the specified conditions. The medium combustion amount is, for example, 50[%] of the high combustion amount. The low combustion amount is, for example, 20[%] of the high combustion amount.

[0040] The control unit 25 sets the combustion amount based on the target steam pressure and the steam pressure of the steam header. The control unit 25 controls the regulating valve 13 based on the combustion amount to adjust the flow rate of fuel supplied to the burner 3. The combustion amount is changed based on the flow rate of fuel supplied to the burner 3. The greater the flow rate of fuel supplied to the burner 3, the higher the combustion amount. The smaller the flow rate of fuel supplied to the burner 3, the lower the combustion amount.

[0041] The control unit 25 controls the output of the blower 4 based on the set combustion amount so that the air ratio becomes an appropriate value. The control unit 25 adjusts the flow rate of fuel supplied to the burner 3 based on the set combustion amount. The control unit 25 estimates the air flow rate based on the detection value of the furnace pressure sensor 9. The control unit 25 adjusts the air ratio by reducing the fuel flow rate in accordance with the reduction in the air flow rate.

[0042] When the combustion amount in the boiler body 2 is changed to a plurality of mutually different combustion amounts, the reference value differs for each combustion amount. In other words, the reference value differs for each combustion load factor of the boiler 1 in operation. The combustion load factor is the ratio of the combustion amount to the rated combustion amount. The rated combustion amount is equal to the high combustion amount. The combustion amount and the combustion load factor correspond one-to-one. The higher the combustion amount, the higher the combustion load factor, and the lower the combustion amount, the lower the combustion load factor.

[0043] As shown in Figure 3, the higher the combustion amount (fuel load factor), the higher the reference value, and the lower the combustion amount (fuel load factor), the lower the reference value. In the example shown in Figure 3, the reference value for low combustion amount is 0.7. The reference value for medium combustion amount is 1.9. The reference value for high combustion amount is 5.5.

[0044] The first real number varies depending on the combustion amount (combustion load rate). The higher the combustion amount (combustion load rate), the smaller the first real number is, and the lower the combustion amount (combustion load rate), the larger the first real number is. In the example shown in FIG. 3, the first real number for a low combustion amount is 1.30. The first real number for a medium combustion amount is 1.20. The first real number for a high combustion amount is 1.10.

[0045] The first relative threshold is a reference value multiplied by a first real number. In the example shown in FIG. 3, the first relative threshold for the low combustion amount is about 0.9. The first relative threshold for the medium combustion amount is about 2.3. The first relative threshold for the high combustion amount is about 6.1.

[0046] When the first real number is a small value, the difference between the reference value and the first relative threshold is small, so that the judgment unit 24 can easily judge whether the furnace pressure value exceeds the first relative threshold. When the first real number is a large value, the difference between the reference value and the first relative threshold is large, so that even if a detection error occurs in the furnace pressure sensor 9, for example, erroneous judgment by the judgment unit 24 is suppressed. In the embodiment, when the combustion amount is low, the first real number is a large value, so that erroneous judgment by the judgment unit 24 is suppressed.

[0047] The first absolute threshold is a predetermined value. In the example shown in FIG. 3, the first absolute threshold for the low combustion amount is 6.5. The first absolute threshold for the medium combustion amount is 6.5. The first absolute threshold for the high combustion amount is 6.5. That is, the first absolute threshold is the same value even if the combustion amount is different. Since the first absolute threshold is the same value regardless of the combustion amount, the calculation load of the controller 10 is reduced. In addition, since the rotation speed of the blower 4 at the low combustion amount and the medium combustion amount is lower than the rotation speed of the blower 4 at the high combustion amount, when soot is present in the flow path, the blower 4 can be adjusted to a high rotation speed to update the reference value. That is, since there is a margin for increasing the rotation speed of the blower 4 at the low combustion amount and the medium combustion amount, when soot is present in the flow path, the rotation speed of the blower 4 can be increased to adjust the flow rate of air sent to the burner 3 to an appropriate amount.

[0048] The first absolute threshold value may be different for the low combustion amount, the medium combustion amount, and the high combustion amount. The first absolute threshold value for the low combustion amount may be lower than the first absolute threshold value for the medium combustion amount, and the first absolute threshold value for the medium combustion amount may be lower than the first absolute threshold value for the high combustion amount.

[0049] FIG. 4 is a diagram showing the relationship between the combustion amount, the reference value, the second real number, the second relative threshold value, and the second absolute threshold value according to the embodiment.

[0050] As shown in Fig. 4, the reference value is higher as the combustion amount (fuel load factor) is higher, and is lower as the combustion amount (fuel load factor) is lower. In the example shown in Fig. 4, the reference value for low combustion amount is 0.7. The reference value for medium combustion amount is 1.9. The reference value for high combustion amount is 5.5. In other words, the reference values ​​shown in Fig. 4 are the same as the reference values ​​described with reference to Fig. 3.

[0051] The second real number is greater than the first real number. The second real number differs for each combustion amount (combustion load rate). The higher the combustion amount (combustion load rate), the smaller the second real number is, and the lower the combustion amount (combustion load rate), the larger the second real number is. In the example shown in FIG. 4, the second real number for a low combustion amount is 1.45. The second real number for a medium combustion amount is 1.35. The second real number for a high combustion amount is 1.15.

[0052] The second relative threshold is a value obtained by multiplying the reference value by a second real number. In the example shown in FIG. 4, the second relative threshold for the low combustion amount is about 1.0. The second relative threshold for the medium combustion amount is about 2.6. The second relative threshold for the high combustion amount is about 6.3.

[0053] At a low combustion amount, the reference value is low, and therefore when the second real number is small, the difference between the reference value and the second relative threshold value is small. In the embodiment, at a low combustion amount, the second real number is large, and therefore the difference between the reference value and the second relative threshold value is large. Therefore, even if a detection error occurs in the furnace pressure sensor 9, for example, erroneous determination by the determination unit 24 is suppressed.

[0054] The second absolute threshold is greater than the first absolute threshold. The second absolute threshold is a predetermined value. In the example shown in FIG. 4, the second absolute threshold for the low combustion amount is 6.9. The second absolute threshold for the medium combustion amount is 6.9. The second absolute threshold for the high combustion amount is 6.9. That is, the second absolute threshold is the same value even if the combustion amount is different. Since the second absolute threshold is the same value regardless of the combustion amount, the calculation load of the controller 10 is reduced. In addition, since the rotation speed of the blower 4 at the low combustion amount and the medium combustion amount is lower than the rotation speed of the blower 4 at the high combustion amount, when soot is present in the flow path, the blower 4 can be adjusted to a high rotation speed to update the reference value. That is, since there is a margin for increasing the rotation speed of the blower 4 at the low combustion amount and the medium combustion amount, when soot is present in the flow path, the rotation speed of the blower 4 can be increased to adjust the flow rate of air sent to the burner 3 to an appropriate amount.

[0055] The second absolute threshold value may be different for the low combustion amount, the medium combustion amount, and the high combustion amount. The second absolute threshold value for the low combustion amount may be lower than the second absolute threshold value for the medium combustion amount, and the second absolute threshold value for the medium combustion amount may be lower than the second absolute threshold value for the high combustion amount.

[0056] Fig. 5 is a diagram illustrating an example of a relationship between a first relative threshold value and a first absolute threshold value according to the embodiment, and Fig. 6 is a diagram illustrating an example of a relationship between a second relative threshold value and a second absolute threshold value according to the embodiment.

[0057] 5, the first real number is determined so that the first relative threshold and the first absolute threshold are equal when the reference value of the high combustion amount is 5.9. In the embodiment, determining whether the reactor pressure value has exceeded the first relative threshold is equivalent to determining whether the reactor pressure value has exceeded the first absolute threshold.

[0058] 6, the second real number is determined so that the second relative threshold and the second absolute threshold are equal to each other when the reference value of the high combustion amount is 6.0. In the embodiment, determining whether the reactor pressure value has exceeded the second relative threshold is equivalent to determining whether the reactor pressure value has exceeded the second absolute threshold.

[0059] In addition, when the reference value is updated to a certain value, the first real number may be determined so that the first relative threshold value and the first absolute threshold value become the same value, and the second real number may be determined so that the second relative threshold value and the second absolute threshold value become the same value. For example, when the reference value for the high combustion amount is updated to a certain value, it may be possible to simultaneously determine whether or not the reactor pressure value has exceeded the first absolute threshold value and to determine whether or not the reactor pressure value has exceeded the second absolute threshold value. In this case, the setting of one of the first and second absolute threshold values ​​may be omitted.

[0060] [Adjustment processing and control unit processing] Fig. 7 is a diagram for explaining the operation of the boiler 1 according to the embodiment. For the sake of simplicity, in the explanation referring to Fig. 7, the first relative threshold value and the second relative threshold value are collectively referred to as the relative threshold value, and the first absolute threshold value and the second absolute threshold value are collectively referred to as the absolute threshold value.

[0061] An absolute threshold value, which is an upper limit value related to the furnace pressure value, is determined in advance and is stored in the absolute threshold value storage unit 23.

[0062] The pressure inside the boiler body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts in a state where there is no soot in the flow path downstream of the burner 3 is detected by the furnace pressure sensor 9. That is, the pressure inside the boiler body 2 when fuel with an air ratio adjusted to an appropriate value is supplied to the burner 3 in a state where there is no soot in the flow path downstream of the burner 3 is detected by the furnace pressure sensor 9. The pressure inside the boiler body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts in a state where there is no soot in the flow path downstream of the burner 3 is stored in the reference value storage unit 21 as an initial reference value.

[0063] The state in which no soot is present in the flow passage downstream of the burner 3 includes the state immediately after a cleaning operation of the flow passage is performed.

[0064] The relative threshold setting unit 22 sets an initial relative threshold by multiplying the initial reference value by a real number greater than one.

[0065] The operation of the boiler 1 is started. The judgment unit 24 monitors the furnace pressure value indicating the pressure inside the boiler body 2 detected by the furnace pressure sensor 9. The judgment unit 24 judges whether or not the furnace pressure value detected by the furnace pressure sensor 9 has exceeded the initial relative threshold value. When it is judged that the furnace pressure value has exceeded the initial relative threshold value, the control unit 25 causes the alarm device 14 to output an alarm indicating that the furnace pressure value has exceeded the initial relative threshold value.

[0066] Furthermore, the determination unit 24 determines whether or not the reactor pressure value detected by the reactor pressure sensor 9 has exceeded the absolute threshold. If it is determined that the reactor pressure value has exceeded the absolute threshold, the control unit 25 causes the alarm device 14 to output an alarm indicating that the reactor pressure value has exceeded the absolute threshold.

[0067] The combustion of fuel in the burner 3 may result in the generation of soot. The generation of soot may narrow the flow path downstream of the burner 3. If the flow path downstream of the burner 3 becomes narrow due to the presence of soot, the pressure inside the boiler body 2 may increase. The alarm device 14 outputs an alarm indicating that the furnace pressure value has exceeded the initial relative threshold value, allowing the operator of the boiler 1 to recognize that soot may be present in the flow path downstream of the burner 3.

[0068] When the air ratio decreases due to narrowing of the flow path caused by the presence of soot, a first adjustment process is performed to increase the output of the blower 4. By performing the adjustment process, the air ratio is returned to an appropriate value even without performing a cleaning operation.

[0069] The first adjustment process may be performed when an alarm indicating that the furnace pressure value has exceeded the initial relative threshold value is output from the alarm device 14. For example, when the determination unit 24 determines that the furnace pressure value has exceeded the initial relative threshold value, the control unit 25 may cause the alarm device 14 to output a message prompting the execution of the first adjustment process. The inspector of the boiler 1 can perform the first adjustment process according to the message output from the alarm device 14.

[0070] In the example shown in FIG. 7, the first adjustment process is performed at the time of the first update. That is, the pressure inside the can body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts at the time of the first update is detected by the furnace pressure sensor 9. At the time of the first update, there is a high possibility that soot is present in the flow path. The pressure inside the can body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts by the first adjustment process is stored in the reference value storage unit 21 as the reference value after the first update. The reference value stored in the reference value storage unit 21 is updated from the initial reference value to the reference value after the first update. If the first adjustment process is performed without performing a cleaning operation, the reference value after the first update will indicate a value higher than the initial reference value.

[0071] The relative threshold setting unit 22 sets a first updated relative threshold by multiplying the first updated reference value by a real number greater than one.

[0072] After the first adjustment process is completed and the reference value stored in the reference value storage unit 21 is updated from the initial reference value to the reference value after the first update, the operation of the boiler 1 is resumed. The determination unit 24 monitors the furnace pressure value indicating the pressure inside the boiler body 2 detected by the furnace pressure sensor 9. The determination unit 24 determines whether or not the furnace pressure value detected by the furnace pressure sensor 9 has exceeded the relative threshold value after the first update. If it is determined that the furnace pressure value has exceeded the relative threshold value after the first update, the control unit 25 causes the alarm device 14 to output an alarm indicating that the furnace pressure value has exceeded the relative threshold value after the first update.

[0073] Furthermore, the determination unit 24 determines whether or not the reactor pressure value detected by the reactor pressure sensor 9 has exceeded the absolute threshold. If it is determined that the reactor pressure value has exceeded the absolute threshold, the control unit 25 causes the alarm device 14 to output an alarm indicating that the reactor pressure value has exceeded the absolute threshold.

[0074] When the air ratio decreases due to narrowing of the flow path caused by the presence of soot, a second adjustment process is performed to increase the output of the blower 4. By performing the adjustment process, the air ratio is returned to an appropriate value even without performing a cleaning operation.

[0075] The second adjustment process may be performed when an alarm indicating that the furnace pressure value has exceeded the relative threshold value of the first update is output from the alarm device 14. For example, when the determination unit 24 determines that the furnace pressure value has exceeded the relative threshold value of the first update, the control unit 25 may cause the alarm device 14 to output a message prompting the execution of the second adjustment process. The inspector of the boiler 1 can perform the second adjustment process based on the message output from the alarm device 14.

[0076] In the example shown in FIG. 7, the second adjustment process is performed at the time of the second update. That is, the pressure inside the boiler body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts at the time of the second update is detected by the furnace pressure sensor 9. The amount of soot present in the flow path at the time of the second update is likely to be greater than the amount of soot present in the flow path at the time of the first update. The pressure inside the boiler body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts by the second adjustment process is stored in the reference value storage unit 21 as the reference value after the second update. The reference value stored in the reference value storage unit 21 is updated from the reference value after the first update to the reference value after the second update. If the second adjustment process is performed without performing a cleaning operation, the reference value after the second update will be higher than the reference value after the first update.

[0077] Thereafter, the third and subsequent adjustment processes are performed in the same manner as the first and second adjustment processes.

[0078] If the adjustment process is performed multiple times without performing cleaning work, the air ratio will be adjusted to the appropriate value, but the amount of soot present in the flow path downstream of burner 3 will gradually increase, and it may eventually become difficult to remove the soot from the flow path.

[0079] In an embodiment, the furnace pressure value exceeding the absolute threshold value indicates that soot is present in the flow path to such an extent that it becomes difficult to remove the soot from the flow path. When the determination unit 24 determines that the furnace pressure value exceeds the absolute threshold value, the control unit 25 causes the alarm device 14 to output a message prompting a cleaning operation of the flow path. The message output from the alarm device 14 enables an inspector of the boiler 1 to perform a cleaning operation of the flow path.

[0080] The control unit 25 may cause the alarm device 14 to output a message prompting the user to perform cleaning of the flow passage when the reactor pressure value exceeds a relative threshold value even if the reactor pressure value does not exceed the absolute threshold value.

[0081] In addition, in Fig. 7, for the sake of simplicity, the first relative threshold and the second relative threshold are collectively referred to as the relative threshold, and the first absolute threshold and the second absolute threshold are collectively referred to as the absolute threshold. As described with reference to Fig. 3 and Fig. 4, the relative threshold includes the first relative threshold and the second relative threshold, and the absolute threshold includes the first absolute threshold and the second absolute threshold.

[0082] When the furnace pressure value exceeds the first relative threshold, the control unit 25 may cause the alarm device 14 to output an alarm indicating that the furnace pressure value has exceeded the first relative threshold while continuing the operation of the boiler 1. When the furnace pressure value exceeds the second relative threshold, the control unit 25 may cause the alarm device 14 to output an alarm indicating that the furnace pressure value has exceeded the second relative threshold and may stop the operation of the boiler 1.

[0083] When the furnace pressure value exceeds the first absolute threshold, the control unit 25 may output a message to the alarm device 14 prompting cleaning of the flow path downstream of the burner 3 while continuing the operation of the boiler 1. When the furnace pressure value exceeds the second absolute threshold, the control unit 25 may output a message to the alarm device 14 prompting cleaning of the flow path downstream of the burner 3 and stop the operation of the boiler 1.

[0084] When the reference value is updated to a certain value, if the first real number is determined so that the first relative threshold value and the first absolute threshold value are the same value, and the second real number is determined so that the second relative threshold value and the second absolute threshold value are the same value, the control unit 25 may output a message prompting cleaning of the flow path downstream of the burner 3 to the alarm device 14 while continuing the operation of the boiler 1 when the furnace pressure value exceeds the first relative threshold value (first absolute threshold value). The control unit 25 may output a message prompting cleaning of the flow path downstream of the burner 3 to the alarm device 14 and stop the operation of the boiler 1 when the furnace pressure value exceeds the second relative threshold value (second absolute threshold value).

[0085] [effect] As described above, the boiler 1 according to the embodiment includes a boiler body 2 having a water tube 11, a burner 3 connected to the boiler body 2, a blower 4 for sending air to the burner 3, a furnace pressure sensor 9 for detecting a furnace pressure value indicating the pressure inside the boiler body 2, and a controller 10. The controller 10 includes a reference value memory unit 21 for storing a reference value indicating the pressure inside the boiler body 2 when the flow rates of fuel and air sent to the burner 3 are adjusted to appropriate amounts, a relative threshold setting unit 22 for setting a first relative threshold value obtained by multiplying the reference value by a first real number greater than 1, an absolute threshold memory unit 23 for storing a first absolute threshold value that is an upper limit value related to the furnace pressure value, and a determination unit 24 for determining whether or not the furnace pressure value exceeds at least one of the first relative threshold value and the first absolute threshold value.

[0086] According to the embodiment, the furnace pressure value changes when soot is present in the flow path downstream of the burner 3. The determination unit 24 determines whether the furnace pressure value exceeds at least one of the first relative threshold value and the first absolute threshold value, so that soot is prevented from accumulating in the flow path to such an extent that it becomes difficult to remove the soot from the flow path.

[0087] In the embodiment, the reference value differs for each combustion load factor (combustion amount) of the operating boiler 1. Therefore, fuel with an air ratio adjusted to an appropriate value for each fuel load factor is supplied to the burner.

[0088] In the embodiment, the higher the combustion load rate (combustion amount), the smaller the first real number. For example, at a low combustion amount, the first real number is a large value, and the difference between the reference value and the first relative threshold value is large. Therefore, even if a detection error occurs in the furnace pressure sensor 9, for example, erroneous determination by the determination unit 24 is suppressed.

[0089] The relative threshold setting unit 22 sets a second relative threshold that is greater than the first relative threshold and the second relative threshold. The absolute threshold storage unit 23 stores the first absolute threshold and the second absolute threshold that is greater than the first absolute threshold. The control unit 25 can cause the alarm device 14 to output a first alarm when the reactor pressure value exceeds the first relative threshold, and can cause the alarm device 14 to output a second alarm different from the first alarm when the reactor pressure value exceeds the second relative threshold. The control unit 25 can cause the alarm device 14 to output a third alarm when the reactor pressure value exceeds the first absolute threshold, and can cause the alarm device 14 to output a fourth alarm different from the third alarm when the reactor pressure value exceeds the second absolute threshold.

[0090] [Other embodiments] FIG. 8 is a schematic diagram of a part of a boiler 1 according to an embodiment. In the example shown in FIG. 8, a damper 15 and a pressure reducing member 16 are arranged in the air passage 5 between the blower 4 and the burner 3. In the above-mentioned embodiment, the output (rotation speed) of the blower 4 is adjusted to adjust the flow rate of air sent to the burner 3. In addition to or instead of adjusting the output of the blower 4, the position (opening) of the damper 15 may be adjusted to adjust the flow rate of air sent to the burner 3. The control unit 25 controls the blower 4 and the damper 15 so that the flow rate of air sent to the burner 3 becomes a flow rate corresponding to the set combustion amount. The pressure reducing member 16 is arranged downstream of the damper 15. The pressure reducing member 16 includes, for example, a punching metal, and reduces the pressure of the air supplied from the blower 4 to the burner 3. The opening of the regulating valve 13 shown in FIG. 1 changes depending on the pressure difference before and after the pressure reducing member 16. The furnace pressure sensor 9 may detect the pressure on the secondary side of the damper 15. The furnace pressure sensor 9 may detect a pressure difference between before and after the pressure reducing member 16. The furnace pressure sensor 9 may detect the pressure on the secondary side of the regulating valve 13 in the fuel supply passage 6.

[0091] In the above-described embodiment, the fuel is gaseous fuel and is combusted in a premixed manner, but the fuel may be combusted in a nozzle-mixed manner. The fuel may also be a liquid fuel such as oil, in which case it may be combusted in a pressure-atomized manner.

[0092] In the above-described embodiment, an economizer may be disposed downstream of the boiler body 2. Even in the case where an economizer is disposed, it is possible to prevent a situation in which it becomes difficult to remove soot from the economizer according to the above-described embodiment.

[0093] In the above-described embodiment, the pressure inside the can body 2 is increased due to soot. For example, the pressure inside the can body 2 may be increased due to unintended obstructions such as corrosion products and condensation. According to the above-described embodiment, it is possible to prevent a situation in which it is difficult to remove the obstructions from the flow path. [Explanation of symbols]

[0094] 1...boiler, 2...boiler body, 3...burner, 4...blower, 5...air blower, 6...fuel supply path, 7...flue, 8...duct, 9...furnace pressure sensor, 10...controller, 11...water pipe, 12...on-off valve, 13...adjusting valve, 14...alarm device, 15...damper, 16...pressure reducing member, 21...reference value memory unit, 22...relative threshold setting unit, 23...absolute threshold memory unit, 24...judgment unit, 25...control unit.

Claims

1. A boiler body having a water tube; a burner connected to the boiler body; A blower for blowing air to the burner; a furnace pressure sensor for detecting a furnace pressure value indicating the pressure inside the boiler body; A controller, The controller: a reference value storage unit that stores a reference value indicating a pressure inside the boiler body when the flow rates of fuel and air sent to the burner are adjusted to appropriate amounts; a relative threshold setting unit that sets a first relative threshold value by multiplying the reference value by a first real number that is greater than 1; an absolute threshold value storage unit that stores a first absolute threshold value that is an upper limit value related to the furnace pressure value; a determination unit that determines whether the reactor pressure value exceeds at least one of the first relative threshold value and the first absolute threshold value, Boiler.

2. The reference value differs depending on the combustion load rate of the boiler during operation. The boiler of claim 1.

3. The first real number is smaller as the combustion load rate is higher. The boiler according to claim 2.

4. the relative threshold setting unit sets a second relative threshold by multiplying the reference value by a second real number that is greater than the first real number; the absolute threshold storage unit stores a second absolute threshold greater than the first absolute threshold, the determination unit determines whether the reactor pressure value exceeds at least one of the second relative threshold value and the second absolute threshold value. The boiler of claim 1.

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