JP2019143904A - Boiler having flame detection device - Google Patents

Abstract

To provide a boiler having a flame detection device which can properly confirm the adaptability of the flame detection device.SOLUTION: A steam boiler 1 for generating steam by combusting a flame by a combustion device 2, and determining the presence or absence of the flame by detecting the flame by the combustion device 2 comprises: an exhaust gas temperature detection device 7 for detecting a temperature of a combustion exhaust gas discharged from the boiler; and a steam temperature detection device 8 for monitoring a temperature of the steam generated from the boiler. The combustion exhaust gas temperature and the steam temperature are compared with each other in advance, and when it is detected that the combustion exhaust gas temperature is dropped lower than the steam temperature after it is detected that the combustion exhaust gas temperature exceeds the steam temperature, combustion by the combustion device 2 is stopped, and the adaptability of the flame detection device is confirmed depending on whether or not the detection of the flame by the flame detection device 4 is changed to flameless detection from a flaming detection.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a boiler having a flame detection device that detects the presence or absence of a flame.

In a combustion apparatus such as a boiler, a flame detection device is installed, and combustion is performed while checking the presence or absence of a flame. When the flame detection device detects that an unexpected flame disappears during the combustion operation, the boiler operation control device stops the fuel supply to stop the combustion. A flame detection device that detects the presence or absence of a flame converts the intensity of light generated by a 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 determination 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 flame, and if the signal value is in the area without flame, it is determined that there is no flame. Like to do.

The judgment value for judging the presence or absence of flame is set in the middle of the state where there is no flame and the state where combustion is stably continued, and the signal value in the case of normal combustion is the area with flame In the state where the flame is extinguished, it is made an area without a flame. If the signal value when there is no flame is small and the signal value when there is a flame becomes large, the signal value is low until ignition, and if the flame immediately after ignition is small, the signal value increases but is lower than that during normal combustion The signal value becomes a large value when the flame is stably burned after a certain amount of time elapses from the value. In the process of increasing the signal value immediately after the start of combustion, the signal value that was in the flame-free region passes the judgment value that determines the presence or absence of flame, and enters the region with flame. Go. Until this judgment value is passed, it is judged that there is no flame, and after passing the judgment value, it is judged 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 can detect an abnormality in the combustion device if an abnormality has occurred in the flame detection device itself. It will disappear. Therefore, confirmation of the appropriateness of the flame detection device itself is performed. To check the adequacy of the flame detector, make sure that the flame is output when the combustion device is combusting, and that there is no flame output when the combustion device stops combustion. By doing. If the operation of the combustion device and the detection by the flame detection device are performed without deviation, it can be determined that the flame detection device is normal.

However, if the continuous combustion time in the combustion device is long and there is no change in the combustion state, the flame detection device is operating properly, or the flame is due to sticking in the control circuit, etc. It cannot be determined that an abnormality has occurred in the detection device and the output with a flame is continued in a state in which it is impossible to detect without a flame. Therefore, Utility Model Registration No. 208285 describes that when the continuous combustion time becomes long, the combustion is temporarily stopped and the detection state by the flame detection device is confirmed at that time. Even in a boiler that performs continuous operation for 24 hours a day, if the operation is periodically stopped to check the suitability of the flame detection device, an abnormality of the flame detection device can be detected. It is safer to stop the combustion to check the adequacy of the flame detection device at short intervals because it is safer to detect the abnormality of the flame detection device earlier, but every time the combustion of the boiler is stopped It would be inconvenient if the boiler's operating rate would be reduced and the steam supply would be hindered. Therefore, it is desired to improve safety while minimizing the combustion stop for checking the 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 checking the appropriateness of the flame detection device. It is in.

A steam boiler for generating steam by heating boiler water in a can by burning a flame with a combustion device, and having a flame detection device for detecting the flame by the combustion device and determining the presence or absence of a flame In order to compare the combustion exhaust gas temperature with the steam temperature, an exhaust gas temperature detection device for detecting the temperature of the combustion exhaust gas discharged from the boiler and a steam temperature detection device for monitoring the temperature of the steam generated from the boiler are provided. After detecting that the combustion exhaust gas temperature has exceeded the steam temperature, if it detects 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. The suitability of the flame detection device is confirmed based on whether or not the change from flame to no flame has been made.

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

The flowchart of the whole boiler in one Example of this invention The graph which showed change of flue gas temperature and steam temperature in one example of the present invention The flowchart which showed the suitability confirmation procedure of the flame detection apparatus in one Example of this invention

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart 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 one embodiment of the present invention. It is the flowchart which showed the appropriateness confirmation procedure of the flame detection apparatus of.

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 downwardly toward the combustion chamber in the center. Yes. 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. Combustion by the combustion device 2 requires fuel and combustion air. Control of fuel supply to the combustion device 2 is performed by opening and closing the fuel control valve 9, and supply of combustion air to the combustion device 2 is performed. This is done by operating the blower 10.

The water pipe surrounding the combustion chamber is installed in an inner and outer double ring, 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. The water pipe facing the combustion gas passage is heated while flowing. The combustion exhaust gas whose temperature has been lowered by heating the water pipe passes through the exhaust passage 12 connected to the side surface of the boiler and is discharged outside.

A water supply pipe 13 is connected to the lower part of the boiler, and water is supplied into 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. When the boiler water is heated in the water pipe, the temperature of the boiler water rises and boiles in the water pipe to generate steam. The generated steam is taken out from the upper part after the liquid component is separated by the steam separator 15 installed in the upper part of the boiler.

The fuel supply to the combustion device 2, the supply of combustion air, the feed water 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 steam supplied by the boiler and the water level in the boiler. In the boiler, the combustion amount 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, and stop, and proportional control that continuously changes the combustion amount. Combustion is stopped when it rises to the upper limit value of the control range, and combustion is started when the steam pressure becomes lower than a predetermined pressure.

A flame detection device 4 for detecting light emitted when the flame 3 is burned in the combustion chamber is installed at the upper part of the boiler in which the combustion device 2 is installed. The flame detection device 4 is connected to a flame detection device control circuit 5 in the operation control device 6, and the flame detection device control circuit 5 determines the presence or absence of a flame. An exhaust gas temperature detection 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 passes, and a steam temperature detection 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.

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 of the boiler 1 is performed, the operation control device 6 performs the control while confirming information on the presence or absence of flame. The operation control device 6 stops the combustion when the flame disappears during the combustion. The 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. Therefore, it is necessary to check the suitability of the flame detection device 4.

FIG. 2 shows changes in the combustion exhaust gas temperature and the steam temperature. The solid line represents the combustion exhaust gas temperature, and the broken line represents the steam temperature. In the figure, it starts from a state in which the combustion is stopped, and at time A during the combustion stop, the steam temperature is 90 ° C. and the gas temperature outside the combustion is 40 ° C.
When combustion by the combustion device 2 is started, the combustion exhaust gas temperature rapidly rises, and then the rate of increase gradually decreases. The steam temperature rises with a slight delay from the start of the rise of the combustion exhaust gas temperature, and the rise of the steam temperature is smaller than the rise of the combustion exhaust gas. Therefore, the combustion exhaust gas temperature that was lower than the steam temperature before the start of combustion is reversed to be higher than the steam temperature by starting combustion, and at time B during combustion, the combustion exhaust gas temperature is 110 ° C., the steam temperature Is 100 ° C. The combustion exhaust gas temperature is relatively low at the start of combustion until the flame stabilizes, so the combustion exhaust gas temperature is relatively low, but higher than the steam temperature.

Thereafter, if combustion is continued, the combustion exhaust gas temperature and the steam temperature will continue to rise gradually, and at time C, the combustion exhaust gas temperature is 210 ° C. and the steam temperature is 170 ° C. When the flame is extinguished in this state, the combustion exhaust gas temperature rapidly decreases, and the steam temperature gradually decreases. 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 again lower than the steam temperature.

When starting combustion with a combustion device that can adjust the amount of combustion, at the start of combustion, combustion is started with a suppressed amount of combustion, and after the flame has stabilized, the amount of combustion is increased. In the boiler, when the temperature of the can rises by continuing combustion, the amount of heat absorbed from the combustion gas decreases. Therefore, time B and time C are both in combustion, but the temperature of the combustion exhaust gas is greatly different. When comparing time B during combustion and time D during combustion stop, the temperature of 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 reversal phenomenon that rises appears. For this reason, it is impossible 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 checking the suitability of the flame detection apparatus. The adequacy of the flame detector is confirmed after the flue gas temperature exceeds the vapor temperature and when the flue gas temperature falls below the vapor 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 a case where combustion is not performed. In this case, the suitability of the flame detection device is not confirmed. The case where the combustion exhaust gas temperature is higher than the steam temperature is a case where combustion is 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 is not possible to determine whether or not combustion is being performed. However, when combustion is performed, the combustion exhaust gas temperature becomes higher than the steam temperature, so the combustion exhaust gas temperature is compared with the steam temperature, and the combustion is detected by detecting that the combustion exhaust gas temperature is higher than the steam temperature. You 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 being performed, but in order to prevent erroneous determination due to sensor error or measurement abnormality, the combustion exhaust gas temperature is It is possible to improve the accuracy of the combustion state by making a determination 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 10 ° C. for 10 seconds.

In the next step S2, the combustion exhaust gas temperature and the steam temperature are compared again. Here, the process waits until the combustion exhaust gas temperature becomes lower than the steam temperature. During combustion, the state where the combustion exhaust gas temperature is higher than the steam temperature is maintained, and when the flame disappears, the combustion exhaust gas temperature rapidly decreases and becomes lower than the steam temperature. Therefore, the time when the combustion exhaust gas temperature exceeds the steam temperature and the combustion exhaust gas temperature falls below the steam temperature can be specified as the time when the combustion has been performed and the flame has disappeared. Also in this case, it is determined based on a value that allows for a margin, for example, it is determined that the flame has disappeared when the combustion exhaust gas temperature is maintained at a temperature lower than the steam temperature by 5 ° C. for 10 seconds. It is possible to prevent misjudgment due to 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. When the fuel control valve 9 is open, the fuel control valve 9 is closed to stop the combustion. 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, the process proceeds to step S5, and it is determined that the flame detection device is normal. However, if the change from the presence of flame to the absence of flame is not performed, 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 adequacy of the flame detection device, after detecting that the combustion exhaust gas temperature exceeded the steam temperature and when the combustion exhaust gas temperature fell below the steam temperature, the combustion device burned. There is a high possibility that the flame will disappear later in the combustion state. At this time, by performing the operation of stopping the fuel supply to the combustion device 2, when the detection state in the flame detection device changes from the presence of flame to the absence of flame, it is determined that the flame detection device is operating normally. Can do. However, at this time, if the detection by the flame detection device did not change without the flame, if the supply of combustion is stopped, the combustion of the flame cannot continue and the flame should have disappeared. Since the flame detection device continues to detect the presence of flame, it can be determined that the flame detection device is abnormal.

The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the art within the technical idea of the present invention.

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

Claims (1)

A steam boiler for generating steam by heating boiler water in a can by burning a flame with a combustion device, and having a flame detection device for detecting the flame by the combustion device and determining the presence or absence of a flame In
An exhaust gas temperature detection device for detecting the temperature of the combustion exhaust gas discharged from the boiler and a steam temperature detection device for monitoring the temperature of the steam generated from the boiler are provided, and the combustion exhaust gas temperature and the steam temperature are compared,
After detecting that the combustion exhaust gas temperature has exceeded the steam temperature, if it is detected 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 starts from the presence of flame. A boiler having a flame detection device, wherein the adequacy of the flame detection device is checked based on whether or not a change to flamelessness has been made.

Images