Combustion control system and abnormality estimation method

Abstract

To estimate a cause of combustion abnormality in a combustion furnace.SOLUTION: A combustion control system comprises: a fuel shut-off valve 2 for supplying a fuel / stopping a supply of a fuel to a burner 11 of a combustion furnace 10; a flame detector 3 for detecting presence of flame in the combustion furnace 10; an ignition device 1 for igniting the burner 11; a burner controller 4 for performing ignition control of the ignition device 1 and opening / closing control of the fuel shut-off valve 2 and determining a state of the fuel shut-off valve 2 and a state of combustion in the combustion furnace 10 on the basis of a signal from the fuel shut-off valve 2 and a signal from the flame detector 3; and an abnormality cause estimation unit 50 for estimating a cause of combustion abnormality in the combustion furnace 10 on the basis of a notification of a determination result by the burner controller 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion control system and an abnormality estimation method for estimating the cause of an abnormality in combustion in a combustion furnace. [Background technology]

[0002] BACKGROUND ART Combustion devices such as combustion furnaces and boilers are equipped with an ignition device and a burner controller as a combustion control system for controlling combustion in the furnace (see Patent Document 1). The ignition device ignites the burner by generating a high voltage of, for example, several kV to several tens of kV in the rod. The burner controller controls the ignition of the burner via the ignition device, monitors the burner combustion, and controls the fuel cutoff valve. When igniting the burner, the burner controller controls the fuel cutoff valve, which starts and stops the supply of fuel to the burner, to supply fuel to the burner, and when stopping combustion by the burner, controls the fuel cutoff valve to stop the supply of fuel to the burner.

[0003] To ensure safe combustion of the burner, a start-up interlock is required to confirm that the conditions for starting the ignition operation are met, and an operation interlock is required to confirm that the conditions for continuing combustion after ignition are maintained.

[0004] Proof of closure (POC) is an interlock input that confirms that the fuel shutoff valve is closed and is used to detect that the fuel shutoff valve is open before fuel is supplied. However, conventional interlock functions do not detect the closure of the fuel shutoff valve while fuel is being supplied, which does not pose a safety risk. As a result, even if a burner misfire or flame failure occurs due to the unintentional closure of the fuel shutoff valve, the operator does not know the cause of the abnormality, and has to investigate the flame detector, fuel supply line, and air supply line, which takes time and effort to determine the cause, resulting in a long recovery time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-121845 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide a combustion control system and an abnormality estimation method that can estimate the cause of an abnormality in combustion in a combustion furnace. [Means for solving the problem]

[0007] The combustion control system of the present invention comprises a fuel cutoff valve configured to supply and stop fuel to a burner of a combustion furnace, a flame detector configured to detect the presence of a flame in the combustion furnace, an ignition device configured to ignite the burner, a combustion control unit configured to control the ignition of the ignition device and control the opening and closing of the fuel cutoff valve, a determination processing unit configured to determine the state of the fuel cutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector, and an abnormality cause estimation unit configured to estimate the cause of an abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit. When the abnormality cause estimation unit is notified by the determination processing unit that the fuel cutoff valve has closed and misfired during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the abnormality is caused by the fuel cutoff valve failing to open. It is characterized by the following.

[0008] The combustion control system of the present invention a fuel cutoff valve configured to supply and stop fuel to a burner of a combustion furnace, a flame detector configured to detect the presence of a flame in the combustion furnace, an ignition device configured to ignite the burner, a combustion control unit configured to control ignition of the ignition device and open / close control of the fuel cutoff valve, a determination processing unit configured to determine the state of the fuel cutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector, and an abnormality cause estimation unit configured to estimate the cause of an abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, The abnormality cause estimation unit is characterized in that when the judgment processing unit notifies the combustion control unit that the fuel shutoff valve has closed and the flame has been cut off during combustion control, the abnormality cause estimation unit estimates that the cause of the abnormality is that the fuel shutoff valve has closed midway. The combustion control system of the present invention a fuel cutoff valve configured to supply and stop fuel to a burner of a combustion furnace, a flame detector configured to detect the presence of a flame in the combustion furnace, an ignition device configured to ignite the burner, a combustion control unit configured to control ignition of the ignition device and open / close control of the fuel cutoff valve, a determination processing unit configured to determine the state of the fuel cutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector, and an abnormality cause estimation unit configured to estimate the cause of an abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit,The abnormality cause estimation unit is characterized in that when the judgment processing unit notifies the combustion control unit that the fuel cutoff valve has closed during combustion control, it estimates that the cause of the abnormality is a failure in the signal output unit of the fuel cutoff valve or the signal input unit of the judgment processing unit. The combustion control system of the present invention a fuel cutoff valve configured to supply and stop fuel to a burner of a combustion furnace, a flame detector configured to detect the presence of a flame in the combustion furnace, an ignition device configured to ignite the burner, a combustion control unit configured to control ignition of the ignition device and open / close control of the fuel cutoff valve, a determination processing unit configured to determine the state of the fuel cutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector, and an abnormality cause estimation unit configured to estimate the cause of an abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, When the judgment processing unit notifies the abnormality cause estimation unit of misfire or flame failure during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the cause of the abnormality is a problem with the supply of air and fuel to the combustion furnace or a malfunction of the flame detector or the ignition device. Moreover, one configuration example of the combustion control system of the present invention is characterized in that it further comprises a notification unit configured to notify an operator of the result of estimation by the abnormality cause estimation unit.

[0009] The abnormality estimation method of the present invention includes a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace, and a second step of estimating the cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result in the first step, wherein the second step notifies the Burna's This method is characterized by including a step of estimating that the cause of the abnormality is that the fuel cutoff valve has failed to open when a notification is received that the fuel cutoff valve has closed and misfired during combustion control by a combustion control unit configured to control the ignition of an ignition device and the opening and closing of the fuel cutoff valve. The abnormality estimation method of the present invention includes a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace, and a second step of estimating the cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result in the first step, wherein the second step notifies the Burna's This method is characterized by including a step of estimating that the cause of the abnormality is the closure of the fuel cutoff valve midway when a notification is received of the closure of the fuel cutoff valve and an extinguishment of the flame during combustion control by a combustion control unit configured to control the ignition of an ignition device and the opening and closing of the fuel cutoff valve. The abnormality estimation method of the present invention includes a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace, and a second step of estimating the cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result in the first step, wherein the second step notifies the Burna's This method is characterized by including a step of estimating that the cause of the abnormality is a malfunction of the signal output unit of the fuel cutoff valve or the signal input unit that acquires a signal from the signal output unit when a notification of closure of the fuel cutoff valve during combustion control is received by a combustion control unit configured to perform ignition control of an ignition device and opening / closing control of the fuel cutoff valve. The abnormality estimation method of the present invention includes a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace, and a second step of estimating the cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result in the first step, wherein the second step notifies the Burna'sWhen a misfire or flame out occurs during combustion control by a combustion control unit configured to control the ignition of an ignition device and the opening and closing of the fuel shutoff valve, the method includes a step of estimating that the cause of the abnormality is a problem with the supply of air and fuel to the combustion furnace or a malfunction of the flame detector or the ignition device. [Effects of the Invention]

[0010] According to the present invention, by providing a determination processing unit and an abnormality cause estimation unit, it is possible to estimate the cause of an abnormality in combustion in a combustion furnace, thereby assisting an operator in restoring the combustion equipment. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of a combustion control system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of a burner controller according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart illustrating the operation of the combustion control system according to the embodiment of the present invention when igniting the burner. [Figure 4] FIG. 4 is a flowchart illustrating the operation of the determination processing unit and the information notification unit of the burner controller according to the embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart illustrating the operation of the higher-level device according to the embodiment of the present invention. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a computer that realizes a combustion control system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will now be described with reference to the drawings. In this embodiment, unintentional closure of the fuel cutoff valve is detected by detecting closure of the fuel cutoff valve using a POC signal, thereby reducing the time required for restoration.

[0013] 1 is a block diagram showing the configuration of a combustion control system according to this embodiment. The combustion control system includes an ignition device 1 that ignites a burner 11 in a combustion furnace 10, a fuel cutoff valve 2 that controls the supply and stop of fuel to the burner 11, a flame detector 3 that detects the presence of a flame in the combustion furnace 10, a burner controller 4 that controls the ignition of the ignition device 1 and the opening and closing of the fuel cutoff valve 2 and determines the state of the fuel cutoff valve 2 during combustion control and the state of combustion in the combustion furnace 10 based on a POC signal from the fuel cutoff valve 2 and a flame signal from the flame detector 3, and a host device 5 that estimates the cause of any abnormality in combustion in the combustion furnace 10 based on a notification of the determination result from the burner controller 4.

[0014] The configuration of the ignition device 1 is disclosed in, for example, Patent Document 1, and therefore a detailed description thereof will be omitted. The flame detector 3 detects the presence of a flame by detecting light emitted from the flame inside the combustion furnace 10. However, detection by light is just one example, and flame detection may be performed by other methods.

[0015] 2 is a block diagram showing the configuration of the burner controller 4. The burner controller 4 includes a combustion control unit 40 that ignites the burner 11 and controls the opening and closing of the fuel cutoff valve 2, a POC signal acquisition unit 41 that acquires a POC signal from the fuel cutoff valve 2, a flame signal acquisition unit 42 that acquires a flame signal from the flame detector 3, a determination processing unit 43 that determines the state of the fuel cutoff valve 2 and the state of combustion in the combustion furnace 10 during combustion control by the combustion control unit 40 based on the POC signal from the fuel cutoff valve 2 and the flame signal from the flame detector 3, and an information notification unit 44 that notifies the host device 5 of the determination result by the determination processing unit 43.

[0016] As shown in FIG. 1, the upper device 5 includes an abnormality cause estimation unit 50 that estimates the cause of the combustion abnormality in the combustion furnace 10 based on a notification from the burner controller 4, and a notification unit 51 that notifies an operator of the estimation result by the abnormality cause estimation unit 50.

[0017] 3 is a flowchart illustrating the operation of the combustion control system of this embodiment when igniting a burner. When an ignition command is received, for example, from an operator of the higher-level device 5, the combustion control unit 40 of the burner controller 4 opens the fuel shutoff valve 2 to start supplying fuel to the burner 11 (step S100 in FIG. 3), and also outputs an ignition command (a voltage for generating a spark by the ignition device 1), thereby igniting the burner 11 by the ignition device 1 (step S101 in FIG. 3).

[0018] Then, when the combustion control unit 40 confirms the presence of a flame in the combustion furnace 10 based on the flame signal acquired from the flame detector 3 via the flame signal acquisition unit 42 (NO in step S102 in FIG. 3), it maintains the opening operation of the fuel cutoff valve 2 (step S103 in FIG. 3). Furthermore, if the combustion control unit 40 cannot acquire a flame signal from the flame detector 3 or the level of the flame signal is low, it determines that an ignition failure (ignition failure) has occurred, in which the ignition does not occur for a certain period of time or more, while outputting the ignition command (YES in step S102), and closes the fuel cutoff valve 2 (step S104 in FIG. 3).

[0019] While combustion is continuing, for example, when an operator of the higher-level device 5 gives an instruction to stop the combustion (YES in step S105 in FIG. 3), the combustion control unit 40 closes the fuel shutoff valve 2 to stop the fuel supply to the burner 11 and stop the combustion in the combustion furnace 10 (step S106 in FIG. 3). Furthermore, if the combustion control unit 40 cannot acquire a flame signal from the flame detector 3 while combustion is continuing, or if the level of the flame signal is low, it determines that a flame failure has occurred, in which the flame goes out after ignition (YES in step S102), and closes the fuel shutoff valve 2 (step S104).

[0020] In this manner, the combustion control unit 40 performs combustion control. Although Fig. 3 does not explicitly state that the output of the ignition command is stopped, the ignition device 1 continuously generates sparks in the ignition electrode rod (not shown) while the ignition command is being output from the burner controller. The combustion control unit 40 stops outputting the ignition command when a predetermined time has elapsed.

[0021] 4 is a flowchart explaining the operation of the determination processing unit 43 and the information notification unit 44 of the burner controller 4. The determination processing unit 43 acquires a POC signal from the fuel cutoff valve 2 via the POC signal acquisition unit 41 (step S200 in FIG. 4). The POC signal is a signal obtained by a POC switch for confirming that the fuel cutoff valve 2 is closed.

[0022] The judgment processing unit 43 judges based on the POC signal whether or not the fuel shutoff valve 2 has been closed while the fuel shutoff valve 2 is being opened and fuel is being supplied to the burner 11 under the control of the combustion control unit 40 (step S201 in FIG. 4). If it is determined that the fuel shutoff valve 2 has closed while fuel is being supplied (YES in step S201), the information notification unit 44 notifies the higher-level device 5 that the closure of the fuel shutoff valve 2 is a minor malfunction (a malfunction that does not require the burner 11 to be stopped) (step S202 in Figure 4).

[0023] In addition, the judgment processing unit 43 judges whether the presence of a flame in the combustion furnace 10 has been confirmed within a certain period of time since the combustion control unit 40 output an ignition command to the ignition device 1, based on the flame signal from the flame detector 3 (step S203 in Figure 4). If the information notification unit 44 is unable to confirm the presence of a flame in the combustion furnace 10 and determines that ignition has occurred (YES in step S203), it notifies the higher-level device 5 of the ignition failure as a serious malfunction (a malfunction that requires the burner 11 to be stopped) (step S204 in Figure 4).

[0024] Furthermore, the determination processing unit 43 determines whether or not a flame failure, in which the flame goes out after ignition has been confirmed, has occurred based on the flame signal (step S205 in FIG. 4). If the fire goes out after ignition is complete and it is determined that the fire has been broken (YES in step S205), the information notification unit 44 notifies the upper device 5 of the fire breaking as a serious malfunction (step S206 in FIG. 4).

[0025] 5 is a flowchart illustrating the operation of the host device 5. Based on the notification from the burner controller 4, the host device 5 estimates the cause of the combustion abnormality in the combustion furnace 10 using the following criteria. First, the abnormality cause estimating unit 50 of the higher-level device 5 acquires notification information from the burner controller 4 (step S300 in FIG. 5).

[0026] If the burner controller 4 notifies the abnormality cause estimation unit 50 that the fuel shutoff valve 2 has closed and then notifies the abnormality cause estimation unit 50 that the misfire has occurred (YES in step S301 of Figure 5), the abnormality cause estimation unit 50 estimates that the cause is that the fuel shutoff valve 2 has malfunctioned and cannot open (step S302 of Figure 5).

[0027] In addition, if the abnormality cause estimation unit 50 receives a notification of flame failure before or after the burner controller 4 notifies it that the fuel shutoff valve 2 has closed (YES in step S303 of Figure 5), it will estimate that the cause is that the fuel shutoff valve 2 closed midway due to, for example, a power supply to the fuel shutoff valve 2 being cut off (step S304 of Figure 5).

[0028] Furthermore, if the burner controller 4 notifies the abnormality cause estimation unit 50 only that the fuel shutoff valve 2 is closed (YES in step S305 of Figure 5), the abnormality cause estimation unit 50 estimates that the cause is a malfunction in the POC signal output unit of the fuel shutoff valve 2 or the POC signal input unit (POC signal acquisition unit 41) of the burner controller 4 (step S306 of Figure 5).

[0029] Furthermore, when the burner controller 4 notifies the abnormality cause estimation unit 50 of misfire or flame failure (step S307 in FIG. 5), the abnormality cause estimation unit 50 estimates that the cause is a problem with the supply of air and fuel to the combustion furnace 10 (for example, fluctuations in the air ratio or fuel supply pressure), or that the flame detector 3 or ignition device 1 has malfunctioned (step S308 in FIG. 5).

[0030] The notification unit 51 of the higher-level device 5 notifies the operator of the estimation result by the abnormality cause estimation unit 50 (step S309 in FIG. 5). The notification method may be a method of displaying the estimation result. It is also possible to provide the abnormality cause estimation unit 50 in the burner controller 4 instead of the host device 5, and configure the burner controller 4 to notify the host device 5 of the estimation result by the abnormality cause estimation unit 50.

[0031] In this way, in this embodiment, the cause of the combustion abnormality in the combustion furnace 10 can be estimated and the estimated result can be notified to the operator. This enables the operator to inspect the combustion equipment (combustion furnace 10, burner 11, ignition device 1, fuel cutoff valve 2, flame detector 3, burner controller 4) based on the notified estimated result, and quickly restore the combustion equipment.

[0032] The burner controller 4 and the higher-level device 5 described in this embodiment can each be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in Figure 6.

[0033] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. In the case of the burner controller 4, the I / F 202 is connected to the ignition device 1, the fuel cutoff valve 2, the flame detector 3, the upper device 5, etc. In the case of the upper device 5, the I / F 202 is connected to the burner controller 4, a display device, etc. A program for realizing the abnormality estimation method of the present invention is stored in the storage device 201. The CPU 200 of each device executes the processing described in this embodiment in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0034] The present invention can be applied to facilities including combustion furnaces. [Explanation of symbols]

[0035] 1...ignition device, 2...fuel shutoff valve, 3...flame detector, 4...burner controller, 5...host device, 10...combustion furnace, 11...burner, 40...combustion control unit, 41...POC signal acquisition unit, 42...flame signal acquisition unit, 43...judgment processing unit, 44...information notification unit, 50...abnormality cause estimation unit, 51...notification unit.

Claims

1. a fuel shutoff valve configured to supply and stop fuel to a burner of the combustion furnace; a flame detector configured to detect the presence of a flame within the combustion furnace; an ignition device configured to ignite the burner; a combustion control unit configured to perform ignition control of the ignition device and opening / closing control of the fuel cutoff valve; a determination processing unit configured to determine a state of the fuel cutoff valve and a state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector; an abnormality cause estimation unit configured to estimate a cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, a combustion control system characterized in that, when notified by the judgment processing unit that the fuel cutoff valve has closed and an ignition has failed during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the cause of the abnormality is that the fuel cutoff valve has failed to open.

2. a fuel shutoff valve configured to supply and stop fuel to a burner of the combustion furnace; a flame detector configured to detect the presence of a flame within the combustion furnace; an ignition device configured to ignite the burner; a combustion control unit configured to perform ignition control of the ignition device and opening / closing control of the fuel cutoff valve; a determination processing unit configured to determine a state of the fuel cutoff valve and a state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector; an abnormality cause estimation unit configured to estimate a cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, a combustion control system characterized in that, when notified by the judgment processing unit that the fuel cutoff valve has been closed and the flame has been cut off during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the cause of the abnormality is that the fuel cutoff valve has been closed midway.

3. a fuel shutoff valve configured to supply and stop fuel to a burner of the combustion furnace; a flame detector configured to detect the presence of a flame within the combustion furnace; an ignition device configured to ignite the burner; a combustion control unit configured to perform ignition control of the ignition device and opening / closing control of the fuel cutoff valve; a determination processing unit configured to determine a state of the fuel cutoff valve and a state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector; an abnormality cause estimation unit configured to estimate a cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, a combustion control system characterized in that, when notified by the judgment processing unit that the fuel cutoff valve has been closed during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the cause of the abnormality is a failure in a signal output unit of the fuel cutoff valve or a signal input unit of the judgment processing unit.

4. a fuel shutoff valve configured to supply and stop fuel to a burner of the combustion furnace; a flame detector configured to detect the presence of a flame within the combustion furnace; an ignition device configured to ignite the burner; a combustion control unit configured to perform ignition control of the ignition device and opening / closing control of the fuel cutoff valve; a determination processing unit configured to determine a state of the fuel cutoff valve and a state of combustion in the combustion furnace based on a signal from the fuel cutoff valve and a signal from the flame detector; an abnormality cause estimation unit configured to estimate a cause of the abnormality in combustion in the combustion furnace based on a notification of the determination result by the determination processing unit, When the determination processing unit notifies the abnormality cause estimation unit of misfire or flame failure during combustion control by the combustion control unit, the abnormality cause estimation unit estimates that the cause of the abnormality is a problem with the supply of air and fuel to the combustion furnace or a malfunction of the flame detector or the ignition device.

5. 5. The combustion control system according to claim 1, The combustion control system further comprises a notification unit configured to notify an operator of the result of estimation by the abnormality cause estimation unit.

6. a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace; a second step of estimating a cause of the abnormality in combustion in the combustion furnace based on the notification of the determination result in the first step, The second step is a method for estimating an abnormality, characterized in that it includes a step of estimating that the cause of the abnormality is that the fuel cutoff valve has malfunctioned and cannot open, when the notification of the judgment result in the first step indicates that the fuel cutoff valve has closed and that ignition has failed during combustion control by a combustion control unit configured to control the ignition of the ignition device of the burner and control the opening and closing of the fuel cutoff valve.

7. a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace; a second step of estimating a cause of the abnormality in combustion in the combustion furnace based on the notification of the determination result in the first step, The second step is a method for estimating an abnormality, characterized in that it includes a step of estimating that the cause of the abnormality is the closure of the fuel cutoff valve midway when the closure of the fuel cutoff valve and the flame cutoff during combustion control by a combustion control unit configured to perform ignition control of the ignition device of the burner and opening and closing control of the fuel cutoff valve are notified as a result of the determination made in the first step.

8. a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace; a second step of estimating a cause of the abnormality in combustion in the combustion furnace based on the notification of the determination result in the first step, The abnormality estimation method is characterized in that the second step includes a step of estimating that the cause of the abnormality is a malfunction of a signal output unit of the fuel cutoff valve or a signal input unit that acquires a signal from the signal output unit when the closure of the fuel cutoff valve during combustion control by a combustion control unit configured to perform ignition control of the ignition device of the burner and opening and closing control of the fuel cutoff valve is notified as a notification of the judgment result by the first step.

9. a first step of determining the state of a fuel shutoff valve and the state of combustion in the combustion furnace based on a signal from the fuel shutoff valve that supplies and stops fuel to a burner of the combustion furnace and a signal from a flame detector that detects the presence of a flame in the combustion furnace; a second step of estimating a cause of the abnormality in combustion in the combustion furnace based on the notification of the determination result in the first step, The second step is an abnormality estimation method characterized in that, when a misfire or flame out during combustion control by a combustion control unit configured to perform ignition control of the ignition device of the burner and opening and closing control of the fuel shutoff valve is notified as a result of the judgment made in the first step, the second step includes a step of estimating that the cause of the abnormality is a problem with the supply of air and fuel to the combustion furnace or a malfunction of the flame detector or the ignition device.

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