JP6984887B2 - Boiler with flame detector - Google Patents

Description

The present invention relates to a boiler having a flame detecting device for detecting the presence or absence of a flame.

In a combustion device such as a boiler, a flame detection device is installed so that the combustion is performed while checking the presence or absence of a flame. When the flame detection device detects that an unexpected flame disappearance occurs during the combustion operation, the operation control device of the boiler stops the fuel supply and stops the combustion. The flame detection device that detects the presence or absence of a flame converts the intensity of the light generated by the flame into an electrical signal such as a resistance value, a current value, or a pulse signal, and determines the presence or absence of a flame according to the signal value. Things are widespread. In the flame detection device, a judgment value for determining the presence or absence of a flame is set, and if the detected signal value is in the area with flame, it is determined that there is a flame, and if the signal value is in the area without flame, it is determined that there is no flame. I try to do.

The judgment value for judging the presence or absence of a flame is set in the middle of the state where there is no flame and the state where combustion is continuously continued stably, and the signal value when normal combustion is performed is in the region where there is a flame. , When the flame is extinguished, it is in the area without flame. When the signal value without flame is small and the signal value with flame is large, the signal value is low until ignition, and when the flame immediately after ignition is small, the signal value is high but lower than that during normal combustion. When it increases from the value and the flame becomes stable and burns after a certain period of time, the signal value also becomes a large value. Immediately after the start of combustion and in the process of increasing the signal value, the signal value that was in the region without flame passes the judgment value for determining the presence or absence of flame, and enters the region with flame. go. It is determined that there is no flame until it passes this determination value, and after it passes the determination value, it is determined that there is a flame.

A flame detection device that detects the presence or absence of a flame is indispensable for detecting an abnormality in the combustion device, and if an abnormality has occurred in the flame detection device itself, it can detect an abnormality in the combustion device. It will disappear. Therefore, the appropriateness of the flame detection device itself is being confirmed. To confirm the suitability of the flame detector, confirm that the output with flame is output when the combustion device is burning, and the output without flame is output when the combustion device is stopped. Do by. If the operation of the combustion device and the detection by the flame detection device are performed without any deviation, the flame detection device can be determined to be normal.

However, if the continuous combustion time in the combustion device becomes long and the combustion state does not change, the flame is caused by whether the flame detection device is operating properly or sticking occurs in the control circuit. It cannot be determined that the output with flame is continued in a state where an abnormality has occurred in the detection device and detection without flame cannot be performed. Therefore, Utility Model Registration No. 208285 describes that when the continuous combustion time becomes long, the combustion is temporarily stopped, and at that time, the detection state by the flame detection device is confirmed. Even in a boiler that operates continuously for 24 hours a day, it is possible to detect an abnormality in the flame detection device by periodically stopping the operation in order to confirm the appropriateness of the flame detection device. It is safer to stop the combustion to confirm the appropriateness of this flame detection device at short intervals because it is safer to detect the abnormality of the flame detection device earlier, but if the combustion of the boiler is stopped each time. It would be inconvenient if the operating rate of the boiler would decrease and the steam supply would be hindered. Therefore, it is desired to improve safety while minimizing combustion stoppage for confirmation of appropriateness.

Utility Model Registration No. 2505285

The problem to be solved by the present invention is to provide a boiler having a flame detection device capable of improving safety while suppressing a decrease in operating rate by appropriately confirming the appropriateness of the flame detection device. It is in.

A steam boiler that heats the boiler water inside the can to generate steam by burning the flame with a combustion device, and has a flame detection device that detects the flame by the combustion device and determines the presence or absence of a flame. In the above, an exhaust gas temperature detector that detects the temperature of the combustion exhaust gas discharged from the boiler and a steam temperature detector that monitors the temperature of the steam generated from the boiler are provided so that the combustion exhaust gas temperature and the steam temperature are compared. If, after detecting that the combustion exhaust gas temperature has exceeded the steam temperature and then detecting that the combustion exhaust gas temperature has fallen below the steam temperature, the combustion by the combustion device is stopped, and the flame detection by the flame detection device has a flame. It is characterized by confirming the appropriateness of the flame detection device depending on whether or not the change from to no flame has been made.

By implementing the present invention and confirming the appropriateness of the flame detection device at an appropriate time, it is possible to detect an abnormality in the flame detection device while minimizing a decrease in the operating rate of the boiler, so that safety is achieved. Can be improved.

Flow diagram of the entire boiler in one embodiment of the present invention A graph showing changes in combustion exhaust gas temperature and steam temperature in one embodiment of the present invention. A flowchart showing a procedure for confirming the appropriateness of the flame detection device in one embodiment of the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of the entire boiler in one embodiment of the present invention, FIG. 2 is a graph showing changes in combustion exhaust gas temperature and steam temperature in one embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. It is a flowchart which showed the appropriateness confirmation procedure of the flame detection apparatus of.

The boiler 1 of FIG. 1 has a combustion chamber in the center and a combustion device 2 in the upper part of the combustion chamber, and the upper combustion device 2 generates a flame 3 downward toward the combustion chamber in the central part. There is. The combustion chamber is a cylindrical space surrounded by a water pipe 11, and heat is generated by burning the flame 3 in the combustion chamber, and the generated heat is absorbed by the water pipe around the combustion chamber. Fuel and combustion air are required for combustion by the combustion device 2. The fuel supply to the combustion device 2 is controlled by opening and closing the fuel control valve 9, and the combustion air is supplied to the combustion device 2. This is done by operating the blower 10.

The water pipes surrounding the combustion chamber are installed in a double ring inside and outside, and the combustion gas enters the combustion gas passage formed between the inner water pipe and the outer water pipe after heating the inner water pipe, and enters the combustion gas passage. It heats the water pipe facing the combustion gas passage while flowing. The combustion exhaust gas whose temperature has been lowered by heating the water pipe is discharged to the outside through the exhaust passage 12 connected to the side surface of the boiler.

A water supply pipe 13 is connected to the lower part of the boiler, and water is supplied to the inside of the boiler by operating a water supply pump 14 installed in the middle of the water supply pipe. The water pipe absorbs the heat generated by the flame 3 and heats the boiler water in the water pipe. By applying heat to the boiler water in the water pipe, the temperature of the boiler water rises, and it boils in the water pipe to generate steam. The generated steam is taken out from the upper part after separating the liquid component by the air-water separator 15 installed in the upper part of the boiler.

Fuel supply to the combustion device 2, supply of combustion air, water supply control to the boiler, and the like are performed by automatic control by the operation control device 6. The operation control device 6 controls the operation of the boiler based on the pressure of the steam supplied by the boiler and the water level in the boiler. In the boiler, the amount of combustion is controlled so that the supplied steam pressure becomes a predetermined pressure. Combustion amount control includes simple ON-OFF control, step control such as high combustion / low combustion / stop, and proportional control that continuously changes the combustion amount, but the steam pressure supplied is Combustion is stopped when the pressure rises to the upper limit of the control range, and combustion is started when the steam pressure becomes lower than the predetermined pressure.

A flame detection device 4 for detecting the light emitted when the flame 3 is burned in the combustion chamber is installed above the boiler in which the combustion device 2 is installed. The flame detection device 4 is connected to the flame detection device control circuit 5 in the operation control device 6, and the presence or absence of the flame is determined by the flame detection device control circuit 5. An exhaust gas temperature detecting device 7 for detecting the temperature of the combustion exhaust gas is provided in the exhaust passage 12 through which the combustion exhaust gas taken out from the boiler is passed, and a steam temperature detecting device 8 for detecting the temperature of the steam is provided in the upper part of the boiler. The combustion exhaust gas temperature detected by the exhaust gas temperature detection device 7 and the steam temperature detected by the steam temperature detection device 8 are also output to the flame detection device control circuit 5.

The information on the presence or absence of flame determined by the flame detection device control circuit 5 is used by the operation control device 6 that controls the operation of the boiler. When the operation control device 6 controls the operation of the boiler 1, the control is performed while confirming the information on the presence or absence of a flame. The operation control device 6 stops combustion when the flame is extinguished during combustion. Combustion can be stopped by closing the fuel control valve 9 and stopping the fuel supply to the combustion device 2. When an abnormality occurs in the flame detection device 4, it is not possible to detect the disappearance of the flame, so it is also necessary to confirm the appropriateness of the flame detection device 4.

FIG. 2 shows changes in the combustion exhaust gas temperature and the steam temperature. The solid line shows the combustion exhaust gas temperature, and the broken line shows the steam temperature. In the figure, it starts from the state where the combustion is stopped, and at the time A when the combustion is stopped, the steam temperature is 90 ° C. and the out-combustion gas temperature is 40 ° C.
When the combustion by the combustion device 2 is started, the temperature of the flue gas rises sharply, and then the rising speed gradually slows down. The steam temperature rises a little after the start of the rise in the combustion exhaust gas temperature, and the rise in the steam temperature is smaller than the rise in the combustion exhaust gas. Therefore, the combustion exhaust gas temperature, which was lower than the steam temperature before the start of combustion, is reversed by the start of combustion and becomes higher than the steam temperature. At time B during combustion, the combustion exhaust gas temperature is 110 ° C. and the steam temperature. Is 100 ° C. At the start of combustion, the minimum amount of combustion is achieved until the flame stabilizes, so the combustion exhaust gas temperature is relatively low, but higher than the steam temperature.

After that, if the combustion is continued, the combustion exhaust gas temperature and the steam temperature continue to rise gradually, and at the time of time C, the combustion exhaust gas temperature becomes 210 ° C. and the steam temperature becomes 170 ° C. When the flame is extinguished in this state, the temperature of the combustion exhaust gas drops sharply, and the steam temperature drops slowly. At time D after the combustion is stopped, the combustion exhaust gas temperature is 140 ° C., the steam temperature is 160 ° C., and the combustion exhaust gas temperature is lower than the steam temperature again.

When starting combustion with a combustion device that can adjust the amount of combustion, combustion is started with a suppressed amount of combustion at the start of combustion, and the amount of combustion is increased after the flame stabilizes. In the boiler, as the temperature of the can body rises by continuing combustion, the amount of heat absorbed from the combustion gas decreases. Therefore, both time B and time C are burning, but the temperatures of the combustion exhaust gas are significantly different. Comparing the time B during combustion and the time D during combustion stop, the temperature of the combustion exhaust gas is higher at time D when combustion is stopped than at time B when combustion is performed and heat is generated. A high reversal phenomenon is appearing. Therefore, it is not possible to determine whether combustion is in progress or combustion is stopped only by the combustion exhaust gas temperature.

FIG. 3 is a flowchart showing a procedure for confirming the appropriateness of the flame detection device. The appropriateness of the flame detection device is confirmed after the temperature of the combustion exhaust gas exceeds the steam temperature and when the temperature of the combustion exhaust gas falls below the steam temperature. In the flowchart, the combustion exhaust gas temperature and the steam temperature are compared in the first step S1. The case where the combustion exhaust gas temperature is not higher than the steam temperature is the case where combustion is not performed, and in that case, the appropriateness of the flame detection device is not confirmed. The case where the combustion exhaust gas temperature is higher than the steam temperature is the case where combustion is being performed, and in that case, the process proceeds to the next step S2.

As shown in FIG. 2, even if the temperature of the combustion exhaust gas is detected, it cannot be determined whether or not combustion is performed by itself. However, when combustion is performed, the combustion exhaust gas temperature becomes higher than the steam temperature. Therefore, by comparing the combustion exhaust gas temperature with the steam temperature and detecting that the combustion exhaust gas temperature is higher than the steam temperature, the combustion is performed. It can detect what is happening. When it is detected that the combustion exhaust gas temperature is higher than the steam temperature, it can be determined that combustion is in progress, but the combustion exhaust gas temperature is set to prevent erroneous judgment due to sensor error or measurement abnormality. It is possible to increase the certainty of the combustion state by making a judgment based on a value that allows for a margin, such as determining that the combustion state is maintained when the steam temperature is maintained at 5 ° C. for 10 seconds.

In the next step S2, the combustion exhaust gas temperature and the steam temperature are compared again, but here, the process waits until the combustion exhaust gas temperature becomes lower than the steam temperature. During combustion, the combustion exhaust gas temperature is maintained higher than the steam temperature, and when the flame disappears, the combustion exhaust gas temperature drops sharply and becomes lower than the steam temperature. Therefore, after the combustion exhaust gas temperature has exceeded the steam temperature and the combustion exhaust gas temperature has fallen below the steam temperature, it can be specified that the combustion is being performed and the flame is extinguished. In this case as well, the sensor is determined based on a value that allows for a margin, such as determining that the flame has disappeared when the combustion exhaust gas temperature is maintained at 5 ° C below the steam temperature for 10 seconds. It is possible to prevent erroneous judgment due to an error or measurement abnormality.

When the combustion exhaust gas temperature becomes lower than the steam temperature in step S2, the process proceeds to the next step S3. Step S3 performs a combustion stop operation, and when the fuel control valve 9 is open, the combustion is stopped by closing the fuel control valve 9. In the next step S4, it is detected whether or not the detection result by the flame detection device is no flame. If the output without flame is performed here, the process proceeds to step S5, and it is determined that the flame detection device is normal. However, if the change from with flame to without flame has not been made, the process proceeds to step S6. In step S6, it is determined that an abnormality has occurred in the flame detection device.

When judging the suitability of the flame detector, if it was detected that the combustion exhaust gas temperature exceeded the steam temperature and the combustion exhaust gas temperature fell below the steam temperature, the combustion device burned. It is more likely that it is the timing when the flame disappears in the combustion state after that. At this time, by performing an operation of stopping the fuel supply to the combustion device 2, if the detection state of the flame detection device changes from the presence of the flame to the absence of the flame, it is determined that the flame detection device is operating normally. Can be done. However, at this time, if the detection by the flame detector did not change without the flame, even though the combustion of the flame could not be continued and the flame should have disappeared when the supply of combustion was stopped. Since the flame detection device continues to detect the presence of flame, it can be determined that the flame detection device is abnormal.

It should be noted that the present invention is not limited to the embodiments described above, and many modifications can be made by a person having ordinary knowledge in the art within the technical idea of the present invention.

1 boiler
2 Combustion device
3 Flame 4 Flame detection device 5 Flame detection device Control circuit 6 Operation control device 7 Exhaust gas temperature detection device 8 Steam temperature detection device
9 Fuel control valve
10 Blower 11 Water pipe 12 Exhaust passage 13 Water supply pipe 14 Water supply pump 15 Air water separator

Claims (1)

A steam boiler that heats boiler water in a can to generate steam by burning a flame with a combustion device, and has a flame detection device that detects the flame by the combustion device and determines the presence or absence of a flame. In
An exhaust gas temperature detector that detects the temperature of the combustion exhaust gas discharged from the boiler and a steam temperature detector that monitors the temperature of the steam generated from the boiler are provided so that the combustion exhaust gas temperature and the steam temperature can be compared.
If it is detected that the combustion exhaust gas temperature has fallen below the steam temperature after detecting that the combustion exhaust gas temperature has exceeded the steam temperature, the combustion by the combustion device is stopped, and the flame detection by the flame detection device is due to the presence of flame. A boiler with a flame detection device, which is characterized by checking the appropriateness of the flame detection device based on whether or not the change to no flame has been made.

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