JP2003130347A - Control method for combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the load following capability of a combustion device. SOLUTION: A control method for the combustion device 2 using a pre-purge operation regulates the pre-purge operation according to a detection result of a leakage state of a fuel valve and a determination result of whether there is an anomaly in a means 9 for detecting the leakage state or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a combustion device.

[0002]

2. Description of the Related Art For example, in a combustion apparatus used for a boiler or the like, when fuel flows into the combustion chamber of the boiler due to leakage of a fuel valve while combustion is stopped, if ignition operation is performed as it is, the combustion chamber inside the combustion chamber Residual gas may catch fire and explode. Therefore, in the combustion apparatus, a so-called pre-purge operation is usually performed in which the residual gas is discharged from the combustion chamber by fresh air from the blower before performing the ignition operation.

By the way, in the combustion apparatus, the ignition operation is started after the pre-purge operation is performed regardless of whether or not fuel is leaked. Therefore, the pre-purge operation improves load followability of the combustion apparatus. It is an obstacle.

[0004]

The problem to be solved by the present invention is to improve the load followability of the combustion apparatus.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first aspect of the present invention is a method for controlling a combustion device for performing a pre-purge operation, which comprises: The pre-purge operation is adjusted based on the detection result of the leak state and the determination result of the presence / absence of abnormality of the means for detecting the leak state.

Further, the invention according to claim 2 is characterized in that, after the combustion is stopped, depending on the result of the detection of the leakage state, the system waits while performing a purge operation with an air volume smaller than the air volume during the pre-purge operation. There is.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The control method of the present invention can be implemented in a combustion device used in a boiler, a heating furnace, or the like. The combustion device includes a fuel supply line and a blower. A fuel valve is provided in the fuel supply line. This fuel valve is normally configured as a double shutoff valve in which two fuel valves are connected in series.

Then, the combustion device is adapted to perform a pre-purge operation before performing an ignition operation. This pre-purge operation is an operation of discharging the residual gas in the combustion chamber by operating the blower with the fuel valve closed. Further, the combustion device is configured to perform a post-purge operation after stopping the combustion operation.
This post-purge operation is similar to the pre-purge operation described above.
It is an operation of discharging the residual gas in the combustion chamber by operating the blower with the fuel valve closed.

Now, the control method of the present invention uses the detection result of the leak state of the fuel valve and the determination result of the presence / absence of abnormality of the means for detecting the leak state (hereinafter referred to as "leak detection means"). It is a control method for adjusting the prepurge operation based on the above. Therefore, the combustion device is provided with the abnormality determination means of the leak detection means.

As the leak detecting means, pressure detecting means, flow rate detecting means, flow velocity detecting means, etc. can be used. By these detecting means, when the fuel valve is closed, by detecting the flow of fuel to the downstream side of the fuel valve, the leak state of the fuel valve, that is, the presence or absence of leak and the leak amount are detected. . Particularly, when the fuel valve is configured as the double cutoff valve, the pressure detecting means can be used as the leak detecting means. In this case, the pressure detection means detects a leak state of each fuel valve by monitoring a change in pressure between the fuel valves when the fuel valves are selectively opened and closed.

The abnormality determining means is configured to determine the abnormality of the leak detecting means based on whether or not the detection signal from the leak detecting means changes when the fuel valve is opened and closed. To do.

Next, the control method of the present invention will be described. In this control method, first, the leak detection means detects the leak state of the fuel valve. The detection of the leak state is performed, for example, when the combustion of the combustion device is stopped or during standby. Next, before the ignition operation is performed, for example, when a combustion request is issued to the combustion device, the abnormality determination means determines whether or not there is an abnormality in the leak detection means. Then, the pre-purge operation is adjusted based on the detection result of the leak state and the determination result of the presence / absence of abnormality. The adjustment of the pre-purge operation based on the detection result and the determination result will be described below.

First, the case where no leak is detected in the fuel valve will be described. In this case, if it is determined that there is no abnormality in the leak detection means, it is possible to confirm that the detection result is correct, so the pre-purge operation is omitted and the ignition operation is performed. On the other hand, if it is determined that the leak detection means is abnormal, it is once detected that there is no leak in the fuel valve, but for safety, the pre-purge operation is performed before the ignition operation is performed. To do.

Next, the case where a leak is detected in the fuel valve will be described. In this case, the detection result of the leak state may be that the leak amount is less than or equal to the allowable value or may be greater than the allowable value. Here, the allowable value is, even if the fuel leaked from the fuel valve flows into the combustion chamber,
It is a value determined based on the amount that does not cause the risk of explosion due to ignition. Now, when the leak amount is less than or equal to the allowable value, the ignition operation is performed after the pre-purge operation regardless of the determination result. Next, when the leak amount is larger than the allowable value, the post purge is continuously performed at the time when the leak of the fuel valve is detected.

As described above, according to the control method of the present invention, when there is no leak in the fuel valve and the leak detection means is normal, safety is confirmed, and the pre-purge operation is omitted. Ignition operation can be performed. Therefore, load followability in the combustion device can be improved. Moreover, by omitting the pre-purge operation, it is possible to reduce the power required for the pre-purge, so that it is possible to save energy.

Next, in the control method of the present invention, another control mode when a leak is detected in the fuel valve will be described. In this control mode, after the combustion is stopped, a control is performed such that a standby operation is performed while performing a purge operation with an air volume smaller than the air volume during the pre-purge operation according to the detection result of the leak state. That is, when the leak amount of the fuel valve is equal to or less than the allowable value, it is a method of performing the minimum necessary purging operation according to the leak amount. By the purging operation, the fuel that has flowed into the combustion chamber during standby can be reliably removed from the combustion chamber, so that explosion due to ignition during the ignition operation can be prevented. Here, in the case of this control mode, when the combustion request is made again, the purging operation is continued until then, so the pre-purge operation can be omitted and the ignition operation can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view schematically showing an example of a boiler for carrying out the present invention, and FIG. 2 is an explanatory view schematically showing a method for detecting a leak state of a fuel valve in the control method of the present invention, Further, FIG. 3 and FIG. 4 are explanatory diagrams schematically showing a method of determining whether or not there is an abnormality in the leak detection means. Here, this embodiment is an embodiment applied to a combustion device in a boiler. The combustion apparatus is an on / off control type combustion apparatus.

First, the basic construction of the boiler will be described with reference to FIG. In FIG. 1, a combustion device 2 is provided above the boiler 1. A fuel supply line 5 having a first fuel valve 3 and a second fuel valve 4 is connected to the combustion device 2. The fuel valves 3 and 4 are provided in series with the fuel supply line 5, and when the combustion operation of the combustion device 2 is started, the both fuel valves 3 and 4 are opened, and when the combustion operation is stopped, the both fuel valves 3 and 4 are opened. The fuel valves 3 and 4 are closed. That is, each of the fuel valves 3, 4
Is configured as a double shutoff valve.

Further, the combustion device 2 is provided with a blower 6 for supplying combustion air and purging air such as pre-purge and post-purge.

Next, the control configuration of the boiler 1 will be described. First, the fuel valves 3 and 4 and the blower 6 are connected to a controller 8 via lines 7, 7 ,. Then, the controller 8 follows the preset program and determines the load condition of the boiler 1,
That is, the combustion control of the boiler 1 is performed by controlling each of the fuel valves 3 and 4 and the blower 6 based on the detected value of the can internal pressure of the boiler 1. That is, the combustion device 2 is controlled to be turned on and off at two positions of combustion and standby according to the can internal pressure.

Here, the basic control contents of the combustion device 2 will be described. First, when the combustion device 2 is operated for combustion, the pre-purge operation is performed by operating the blower 6 with the fuel valves 3 and 4 closed. Then, after performing the pre-purge operation for a predetermined time, the both fuel valves 3 and 4 are opened, the ignition operation is performed, and the combustion operation is started. Next, when the combustion operation is ended, both fuel valves 3 and 4 are closed to extinguish the fire. And
After the fuel valves 3 and 4 are closed, the blower 6 is operated for a predetermined period of time to perform the post-purge operation.

Next, the leak state detecting means (hereinafter referred to as "leak detecting means") 9 of each of the fuel valves 3 and 4 used in the control method of the present invention and the abnormality of the leak detecting means 9 are detected. The presence / absence determining means (hereinafter referred to as “abnormality determining means”) 10 will be described.

First, the leak detecting means 9 is a pressure detecting means and is provided between the fuel valves 3 and 4 in the fuel supply line 5. The leak detection means 9 is
Is connected to the controller 8 via the line 7,
The controller 8 can monitor changes in pressure between the fuel valves 3 and 4. Then, the leak detection means 9 leaks the fuel valves 3 and 4 based on the change in pressure between the fuel valves 3 and 4 when the fuel valves 3 and 4 are selectively opened and closed. It is designed to detect conditions.

Next, a method of detecting the leak state of each of the fuel valves 3 and 4 will be described with reference to FIG. First, the leak state of each of the fuel valves 3 and 4 is detected when the combustion of the combustion device 2 is stopped and when the post-purge operation is performed. First, the fuel valves 3 and 4 are closed to end the combustion operation. At this time, first, the upstream first fuel valve 3 is closed, and after the first set time A, the downstream second fuel valve 4 is closed. When the second fuel valve 4 is closed,
The pressure between the fuel valves 3 and 4 becomes the pressure in the combustion chamber of the boiler 1 (hereinafter referred to as “furnace pressure”). Then, during the second set time B, the state where both the fuel valves 3 and 4 are closed is maintained. Next, while the second set time B elapses,
The leak detection means 9 monitors changes in pressure between the fuel valves 3 and 4. In this state, if the pressure between the fuel valves 3 and 4 does not change (shown by the solid line in FIG. 2), it is determined that there is no leak in the first fuel valve 3. On the contrary, when the pressure between the fuel valves 3 and 4 increases (see FIG. 2).
(Indicated by a dotted line), it is determined that the first fuel valve 3 is leaking.

Next, after the second set time B has elapsed, the first fuel valve 3 is once opened and then closed again. Then, when the first fuel valve 3 is closed again, the both fuel valves 3, 4
The pressure between them becomes the fuel supply pressure in the fuel supply line 5. The fuel supply pressure (hereinafter, simply referred to as “supply pressure”) is higher than the furnace pressure. Then, during the third set time C, the state where both the fuel valves 3 and 4 are closed is maintained. While the third set time C has elapsed, the leak detection means 9 monitors the change in pressure between the fuel valves 3 and 4. In this state, if the pressure between the fuel valves 3 and 4 does not change (shown by the solid line in FIG. 2), it is determined that the second fuel valve 4 does not leak. On the contrary, when the pressure between the fuel valves 3 and 4 decreases (shown by the one-dot chain line in FIG. 2), it is determined that the second fuel valve 4 is leaking.

When it is determined that one or both of the fuel valves 3 and 4 has no leakage based on the result of the determination as to whether or not the fuel valves 3 and 4 are leaking, the fuel valves 3 and 4 are not leaked. It is judged that there is no fuel leakage from the combustion chambers 3 and 4 to the combustion chamber. On the other hand, when it is determined that the fuel valves 3 and 4 are leaking, it is determined that fuel is leaking to the combustion chamber.

Further, when a leak is detected in both the fuel valves 3 and 4, the leak detecting means 9 detects whether or not the leak amount at this time is less than or equal to an allowable value. That is, the time D from when the first fuel valve 3 is closed again until the pressure between the fuel valves 3 and 4 is reduced to a predetermined pressure, for example, the furnace pressure, is measured. The leak amount is detected based on Here, the allowable value is a value determined based on the amount of fuel that has leaked from each of the fuel valves 3 and 4 and has no risk of explosion due to ignition even if the fuel flows into the combustion chamber.

Next, the abnormality determining means 10 will be described. The abnormality determining means 10 includes the fuel valves 3, 4
Is selectively opened / closed, the presence / absence of abnormality is determined based on the change in the detection signal from the leak detection means 9. Therefore, in this embodiment, the abnormality determination means 10 is stored in the controller 8 as software.

Next, a method of determining the presence / absence of abnormality by the abnormality determining means 10 will be described with reference to FIGS. 3 and 4. The abnormality determining means 10 is adapted to determine whether or not there is an abnormality in the leak detecting means 9 after detecting the leak state of the both fuel valves 3 and 4, and this determining method uses the both fuel valves 3 and 4. , 4 is not detected and the case where the leakage is detected is different. First, the case where no leak is detected in both fuel valves 3 and 4 will be described with reference to FIG. In this case, the second fuel valve 4 is once opened with the first fuel valve 3 closed, and then closed again. When the pressure between the fuel valves 3 and 4 changes from the supply pressure to the furnace pressure when the second fuel valve 4 is closed again (illustrated by a solid line in FIG. 3)
Determines that the leak detection means 9 is normal. On the contrary, if the pressure between the fuel valves 3 and 4 remains unchanged at the supply pressure (shown by the chain double-dashed line in FIG. 3), it is determined that the leak detection means 9 is abnormal.

Next, the case where the leakage of the fuel valves 3 and 4 is detected will be described with reference to FIG. In this case, the first fuel valve 3 is once opened with the second fuel valve 4 closed, and then closed again. When the pressure between the fuel valves 3 and 4 rises when the first fuel valve 3 is closed again (shown by the solid line in FIG. 4), it is determined that the leak detection means 9 is normal. . On the contrary, when the pressure between the fuel valves 3 and 4 does not change (shown by the chain double-dashed line in FIG. 4), it is determined that the leak detection means 9 is abnormal.

Next, the control method of the present invention will be described together with the control contents of the controller 8. First, when the combustion of the combustion device 2 is stopped, the controller 8 detects the leakage of the fuel valves 3 and 4 by the leakage detection means 9 during the post-purge operation. Then, when there is a combustion request to the combustion device 2, the abnormality determination means 10 determines the abnormality of the leak detection means 9.
Then, the pre-purge operation is adjusted based on the detection result of the leak state and the determination result of the presence / absence of abnormality of the abnormality determination means 10. Next, the adjustment of the pre-purge operation based on the detection result and the determination result will be described in detail.

First, the case where the leak detection means 9 detects no leak in the fuel valves 3 and 4 will be described. In this case, when a combustion request is made to the combustion device 2, the abnormality determination means 10 determines whether or not there is an abnormality in the leak detection means 9. If there is no abnormality in the leak detection means 9, the pre-purge operation is omitted, the ignition operation is performed, and the combustion operation is performed. On the other hand, when there is an abnormality in the leak detection means 9, it is once detected that there is no leak in the fuel valves 3 and 4, but the detection result cannot be trusted, so the pre-purge operation is performed. Then, the ignition operation is performed.

Next, the case where a leak is detected in each of the fuel valves 3 and 4 will be described. In this case, as described above, the detection result of the leakage state may be that the leakage amount is less than or equal to the allowable value or greater than the allowable value. First,
When the leakage amount is less than or equal to the allowable value, the pre-purge operation is started when the combustion request is made. And
During the pre-purge operation, the abnormality determination means 10 determines whether or not there is an abnormality in the leak detection means 9. And
Ignition is performed after the pre-purge operation regardless of the determination result of the presence or absence of abnormality of the leak detection means 9. Here, when it is determined that the leak detection unit 9 is abnormal, the fact is notified.

Next, when the leakage amount is larger than the allowable value, the post-purge operation is continued at the time when the leakage of each of the fuel valves 3 and 4 is detected, and thereafter the ignition operation is performed. Prevent the transition. Then, an abnormality indicating that a leak has occurred in each of the fuel valves 3 and 4 is notified.

As described above, according to this control method, when there is no leak in the fuel valves 3 and 4 and the leak detection means 9 is normal, safety is confirmed and the pre-purge operation is omitted. Thus, the ignition operation can be performed. Therefore, the load followability in the combustion device 2 can be improved. Moreover, by omitting the pre-purge operation, it is possible to reduce the power required for the pre-purge, so that it is possible to save energy.

Next, another control mode when a leak is detected in each of the fuel valves 3 and 4 will be described. In this control mode, after the combustion is stopped, the combustion device 2 is controlled to stand by while performing a purging operation with an air volume smaller than the air volume during the pre-purge operation according to the detection result of the leak state. That is, each of the fuel valves 3,
When the leakage amount of No. 4 is less than or equal to the allowable value, fuel is removed from the combustion chamber by continuously performing the minimum required purging operation according to the leakage amount while the combustion device 2 is on standby. Then, it is possible to prevent explosion due to ignition during the ignition operation. Here, in the case of this control mode, when the combustion request is made again, the pre-purge operation can be omitted.

[0037]

According to the present invention, the load followability of the combustion device can be improved and energy saving can be achieved. In addition, it is possible to perform safety-controlled control according to the degree of leakage of the fuel valve.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an example of a boiler for carrying out the present invention.

FIG. 2 is an explanatory view schematically showing a method for detecting a leak state of a fuel valve according to the present invention.

FIG. 3 is an explanatory view schematically showing a method of determining whether or not there is an abnormality in the leak detection means when there is no leak in the fuel valve in the present invention.

FIG. 4 is an explanatory view schematically showing a method for determining whether or not there is an abnormality in the leak detection means when a leak has occurred in the fuel valve in the present invention.

[Explanation of symbols]

2 Combustion device 3 First fuel valve (fuel valve) 4 Second fuel valve (fuel valve) 9 Leakage detection means

Claims (2)

[Claims] 1. A method of controlling a combustion device 2 for performing a pre-purge operation, the method being based on a detection result of a leak state of a fuel valve and a determination result of abnormality of a means 9 for detecting the leak state. A method for controlling a combustion device, comprising adjusting a prepurge operation. 2. The combustion apparatus according to claim 1, wherein after the combustion is stopped, a standby operation is performed while performing a purging operation with an air volume smaller than the air volume during the pre-purge operation according to a detection result of the leak state. Control method.