JP7725914B2 - Combustion equipment - Google Patents

Description

The present invention relates to a combustion device.

Combustion devices are equipped with flame detection means that detect whether a burner flame is occurring. This flame detection means detects the presence or absence of a burner flame and controls the burner combustion according to the detection result. Some flame detection means use an ultraviolet detector to detect the flame. However, if the ultraviolet detector deteriorates, it may self-discharge and erroneously detect the presence of a flame even when there is no flame. To identify such erroneous detections, for example, a shutter that can be opened and closed is provided between the burner and the ultraviolet detector. Even if the ultraviolet detector determines that a flame is present, closing the shutter to block light and maintaining the flame presence determination makes it possible to identify that the ultraviolet detector has deteriorated and therefore detected the erroneous detection (see, for example, Patent Document 1).

Special Publication No. 6-100332

However, the shutters in conventional combustion devices operate physically. As a result, there was a problem in that if the shutter operated more frequently, the lifespan of the shutter mechanism would be shortened accordingly.

The present invention was conceived in light of these circumstances, and its purpose is to provide a combustion device that can stably identify erroneous flame detection due to deterioration of the flame detection means over the long term.

In order to achieve the above object, a fuel system according to one aspect of the present invention comprises a burner that generates a flame, an ignition device that ignites the burner, flame detection means that detects the presence or absence of a flame in the burner, concentration detection means that detects the concentration of a detection target gas contained in gas after combustion by the flame, and control means that performs predetermined misfire control when it is determined that no flame is occurring based on a result of comparing the concentration detected by the concentration detection means with a predetermined threshold value even when the presence of a flame is detected by the flame detection means at an ignition timing when ignition processing for igniting the burner is performed , and The system further comprises a shading means which detects the presence or absence of a flame and is switchable between a blocking state in which the flame light is blocked from entering the flame detection means and a non-blocking state in which the flame light is not blocked from entering the flame detection means, and a determination means which, when the presence of a flame is detected by the flame detection means at the ignition timing and it is determined that no flame has occurred based on the result of comparing the concentration detected by the concentration detection means with a predetermined threshold, switches the shading means to the blocking state to determine whether the presence of a flame has still been detected by the flame detection means, and the control means performs the misfire control when it is determined by the determination means that the presence of a flame is still detected.

With the above configuration, the concentration detection means does not physically operate, so even if the concentration of the gas to be detected is frequently detected, the impact on the lifespan of the concentration detection means is minimal. This makes it possible to stably determine, over the long term, whether or not a flame is detected erroneously when the flame detection means detects the presence of a flame.

Furthermore, when it is determined that no flame is present based on the comparison result between the concentration detected by the concentration detection means and a predetermined threshold, the light blocking means is switched to the blocking state, and it is possible to determine whether the detection by the flame detection means is an erroneous detection. This reduces the frequency of switching the light blocking means, and when the flame detection means detects the presence of a flame, it is possible to stably determine over the long term whether the detection is an erroneous detection.

Preferably, the misfire control is a control that stops the combustion process, and when the determination means determines that no flame is detected, the control means continues the combustion process while performing notification control to notify the user that no flame has been detected based on the comparison result between the concentration detected by the concentration detection means and a predetermined threshold value.

With the above configuration, when the determination means determines that no flame has been detected and it is determined that the detection by the flame detection means is not an erroneous detection, only notification control is performed and combustion is allowed to continue, thereby maintaining combustion efficiency.

Preferably, if the determination means determines that no flame has occurred based on the comparison result between the concentration detected by the concentration detection means and a specific value even after the ignition timing, the determination means sets the light blocking means to the blocking state to determine whether the flame detection means has still detected the presence of a flame.

With the above configuration, even after the ignition timing, the concentration detection means can be used to determine whether the detection by the flame detection means is an erroneous detection.

FIG. 1 is a diagram schematically illustrating the configuration of a boiler in which a combustion device is used. 10 is a flowchart illustrating an example of a flame determination process.

The combustion device according to the present disclosure is a combustion device used in boilers, etc. The combustion device will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope of the claims are intended to be included in the present invention.

<Overview of the configuration>
A boiler 1 equipped with a combustion device according to an embodiment of the present invention will be described below with reference to Fig. 1. Fig. 1 is a diagram schematically showing the configuration of a boiler 1 equipped with a combustion device according to an embodiment of the present invention.

The boiler 1 includes a boiler body 2 that burns fuel to generate steam, a blower 3 that sends air into the boiler body 2 via an air supply path 30, a flue 4 that extracts exhaust gases from the boiler body 2, a fuel supply line 5 that supplies fuel to the boiler body 2, a control unit 6 that controls the operation of the boiler 1, a flame detector 7a (an example of a flame detection means) that detects the presence or absence of a flame, a shading device 7b (an example of a shading means), a pilot burner 8 (an example of a burner), an ignition device 9, a main burner 20, and a gas detection device 10 (an example of a concentration detection means). The combustion device includes the control unit 6, the flame detector 7a, the shading device 7b, the pilot burner 8, the ignition device 9, the main burner 20, and the gas detection device 10. While the fuel is described as a gas in this example, it is not limited to gases such as gas, and may also be a liquid such as oil.

The main burner 20 is located at the connection between the boiler body 2 and the air supply passage 30, and combustion air is supplied from the blower 3 via the air supply passage 30. The pilot burner 8 is located so that its tip is close to the main burner 20 and can ignite the main burner 20.

The fuel supply line 5 includes a fuel supply line 5a that connects to the air supply line 30 and a fuel supply line 5b that branches off and connects to the pilot burner 8. The fuel supplied from the fuel supply line 5a to the air supply line 30 is mixed with air blown from the blower 3 and supplied to the main burner 20 in the boiler body 2. The fuel supplied from the fuel supply line 5b to the pilot burner 8 is mixed in the pilot burner 8 with air supplied from the pilot air supply line 30a, which branches off upstream from the air supply line 30. The fuel supply line 5a is provided with on-off valves (solenoid valves) 11 and 12 for opening and closing the flow path, and a fuel supply rate adjustment valve 13. The fuel supply rate adjustment valve 13 functions as a pressure adjustment valve that can adjust the flow rate of fuel supplied to the boiler body 2, and also has a shut-off function. The fuel supply rate adjustment valve 13 is provided downstream of the on-off valves 11 and 12 and is a motor valve whose opening is adjusted by the control unit 6. The fuel supply amount adjustment valve 13 is not limited to a motor valve as long as it adjusts the flow rate of fuel; it may also be, for example, an air-operated control valve. Furthermore, the fuel supply line 5b is provided with on-off valves (solenoid valves) 14 and 15 for opening and closing the flow path.

The ignition device 9 is an ignition device (igniter) that generates a spark to ignite the pilot burner 8, and is provided in the air supply passage 30. The pilot burner 8 is ignited by the spark generated by the ignition device 9, generating a flame. This flame ignites the main burner 20, causing fuel to burn within the boiler body 2.

The flame detector 7a is positioned so that it can detect at least the presence or absence of a flame from the pilot burner 8. The flame detector 7 is an optical detection device such as an ultraviolet photocell, cadmium sulfide cell, or lead sulfide cell, and detects the flame as light (including visible and invisible light). While an ultraviolet detector such as an ultraviolet photocell that detects the presence or absence of a flame based on ultraviolet light is preferred as the flame detector 7, it is not limited to this and may also be a detector that detects visible light or infrared light. Among detectors, ultraviolet detectors are preferred because they can be used without being placed directly in the flame, are less susceptible to contamination due to the adhesion of soot, and are highly durable. In addition, they are less sensitive to the red heat of the furnace walls than detectors that detect visible light or infrared light, and have high accuracy in detecting blue flames.

The shading device 7b is located between the position where the flame of the pilot burner 8 is generated and the flame detector 7a. While Figure 1 shows an example in which the flame detector 7a is located a predetermined distance from the shading device 7b, the flame detector 7a and the shading device 7b may be located close to each other, with the flame detector 7a located immediately before (for example, adjacent to) the shading device 7b (either integrated or separate). The shading device 7b is composed of a shutter that can be repositioned based on a control signal from the control unit 6 between a blocking position (blocking state) that blocks the light of the flame of the pilot burner 8 from reaching the flame detector 7a, and a non-blocking position (non-blocking state) that does not block the light of the flame from reaching the flame detector 7a.

The gas detection device 10 is installed at a predetermined position in the flue 4. The gas detection device 10 is equipped with a gas sensor, and is configured to detect the exhaust gas extracted from the flue 4 as the detection target gas using the gas sensor. The gas detection device 10 is also configured to return the exhaust gas extracted from the flue 4 back to the flue 4. An example of the gas sensor is one that detects the concentration of carbon monoxide contained in the extracted gas (exhaust gas).

The control unit 6 is realized by a computer that includes an internal memory, timer, and processing unit. The control unit 6 adjusts the fuel supply flow rate from the fuel supply line 5a to the air supply passage 30 (and thus the main burner 20) based on the combustion air supply flow rate to the boiler main body 2, depending on the stage of combustion. That is, if the combustion air flow rate increases, the opening of the fuel supply amount adjustment valve 13 is increased to increase the fuel flow rate. On the other hand, if the combustion air flow rate decreases, the opening of the fuel supply amount adjustment valve 13 is decreased to decrease the fuel flow rate. The control unit 6 also controls whether or not fuel is supplied to the pilot burner 8 from the fuel supply line 5b by controlling the opening and closing of the on-off valves 14 and 15. The control unit 6 controls the supply of fuel to the pilot burner 8 for combustion even when the main burner 20 is burning (when there is a load), but this is not limiting; it may also control the supply of fuel not to the pilot burner 8 when the main burner 20 is burning, and to supply fuel to the pilot burner 8 for combustion when combustion is not required in the main burner 20 (when there is no load). The control unit 6 also has a flame determination function.

The flame determination function of the control unit 6 is a function that determines whether or not a flame is occurring in at least the pilot burner 8. In the first stage, the control unit 6 determines whether or not a flame is occurring in the pilot burner 8 based on the detection results of the flame detector 7a.

Furthermore, when the control unit 6 detects the presence of a flame in the pilot burner 8 through the first-stage determination, it performs a second stage to determine the presence or absence of a flame in the pilot burner 8 based on whether the concentration detected by the gas detection device 10 is a specific concentration that can be assumed when a flame is present. It has been confirmed that the concentration of carbon monoxide in the exhaust gas momentarily exceeds a predetermined threshold value when the pilot burner 8 actually ignites, and that it reaches an abnormal value (specific value) when a flame goes out during combustion operation. Taking note of this phenomenon, in a second stage, separate from the first-stage determination, the gas detection device 10 is used to compare the concentration of the gas to be detected (e.g., carbon monoxide) in the exhaust gas with a predetermined threshold value or an abnormal value to determine the presence or absence of a flame in the pilot burner 8.

Furthermore, when the second stage judgment does not detect the presence of a flame on the pilot burner 8, that is, when there is a discrepancy between the first stage judgment result and the second stage judgment result, the control unit 6 operates the shutter to block the light from the shading device 7b in the third stage, and judges whether the detection result of the flame detector 7a still detects the presence of a flame on the pilot burner 8, that is, whether the flame detector 7a has made an erroneous detection. This determines whether the flame detector 7a has made an erroneous detection, etc.

The control unit 6 determines whether or not to supply fuel to the main burner 20 based on the results of the flame determination function. That is, the flame determination function monitors the presence or absence of a flame, and when it determines that a flame is occurring in the pilot burner 8, for example, at ignition, it starts fuel supply to the main burner 20 and starts combustion by the combustion device. This prevents fuel supply from being started even when no flame is occurring in the pilot burner 8 due to a false detection by the flame detector 7a.

<Flame detection process>
The flame determination process performed by the control unit 6 will be described with reference to FIG. 2. FIG. 2 is a flowchart illustrating an example of the flame determination process. The flame determination process is repeatedly executed by the control unit 6 at predetermined time intervals (e.g., one second). In step S10, it is determined whether or not it is the ignition timing at which ignition processing has been performed to ignite a burner (e.g., pilot burner 8) that is the target of flame detection by the flame detector 7a. If it is determined that it is the ignition timing, then in step S11, it is determined whether or not a flame is present, based on the detection result by the flame detector 7a. If it is not determined that a flame is present in step S11, it is highly likely that ignition has not occurred because the processes of steps S20 to S24 described below have been performed. Therefore, in step S16, misfire control (e.g., not starting combustion or stopping combustion) is performed.

On the other hand, if it is determined in step S11 that a flame is present, the second stage of determination is performed in step S12, where it is determined based on the detection results of the gas detection device 10 whether the carbon monoxide concentration in the exhaust gas exceeds a predetermined threshold that can be reached when ignition occurs. If it is determined in step S12 that the predetermined threshold has been exceeded, the first stage determination result and the second stage determination result are consistent, and the flame determination process is terminated. In contrast, if it is not determined in step S12 that the predetermined threshold has been exceeded, there is a discrepancy between the first stage determination result and the second stage determination result, and the process proceeds to the third stage of determination. First, in step S13, the light blocking device 7b is controlled to a blocked state. Next, in step S14, it is determined whether it is still determined that a flame is present based on the detection results of the flame detector 7a.

If it is not determined in step S14 that there is a flame, the flame detector 7a has detected no flame in the shut-off state, which is normal. However, there is a possibility that an abnormal concentration alarm has been issued in the gas detection device 10, so a concentration abnormality alarm is issued in step S15. Even if a concentration abnormality alarm is issued, there is a high possibility that the concentration is temporarily abnormal due to an external factor, so the combustion process is continued and maintained. In contrast, if it is still determined that there is a flame in step S14, the flame detector 7a has detected the presence of a flame even in the shut-off state, which is abnormal, so misfire control is performed. In this case, a flame detector abnormality alarm may be issued to indicate that an abnormality has occurred in the flame detector 7a, as in step S24 described below.

Returning to step S10, if it is not determined that it is time to ignite, step S20 determines whether combustion driving is already in progress (for example, a state in which the control unit 6 is controlling the on-off valves 14 and 15 to an open state). If it is determined in step S20 that combustion driving is in progress, step S21 determines whether a flame is present based on the detection results from the flame detector 7a. If a flame is not present in step S21, it is highly likely that a misfire has occurred, and therefore misfire control is performed in step S16.

On the other hand, if step S21 determines that a flame is present, step S22 determines whether the carbon monoxide concentration in the exhaust gas is at an abnormal value, which is possible when a fire has occurred, based on the detection result from gas detection device 10. If step S22 does not determine that the concentration is at an abnormal value, the determination results from steps S21 and S22 are consistent, and the flame determination process ends. On the other hand, if step S22 determines that the concentration is at an abnormal value, a discrepancy occurs between the determination results from steps S21 and S22, and the process proceeds to step S13 to perform a determination using light blocking device 7b.

When it is not determined in step S20 that combustion is in progress, that is, when combustion is stopped and not during ignition or combustion, and under circumstances where a flame would not normally be detected, step S23 determines whether a flame is present based on the detection results from flame detector 7a. If a flame is not detected in step S23, the flame detector 7a is normal, and the flame detection process ends. On the other hand, if a flame is detected in step S23, it is clear that an abnormality has occurred in the flame detector 7a, and therefore a flame detector abnormality alarm is issued in step S24 to indicate that an abnormality has occurred in the flame detector 7a, regardless of the detection results of the gas detection device 10.

In a boiler 1 equipped with a combustion device according to this embodiment, at the timing of ignition, a determination is made in step S11 of FIG. 2 that a flame is present based on the detection results from the flame detector 7a. Then, in step S12, a determination is made in step S13 that a flame is not present based on the detection results from the gas detection device 10, indicating that the concentration does not exceed a predetermined threshold. Consequently, in step S13, the light blocking device 7b is controlled to a shutoff state. If a determination is made in step S14 that a flame is still present based on the detection results from the flame detector 7a, an abnormality in the flame detector 7a is assumed, and misfire control is performed in step S16. Because the gas detection device 10 does not physically operate, frequent detection of the carbon monoxide concentration in the exhaust gas, which is the target gas, has little impact on the life of the gas detection device 10. Meanwhile, the frequency with which the light blocking device 7b is controlled to a shutoff state can be reduced. As a result, when a flame is detected by the flame detector 7a, it is possible to stably determine, over the long term, whether the detection is a false positive.

Furthermore, if it is not determined in step S14 that a flame is present based on the detection results from the flame detector 7a, the combustion process continues while an abnormal concentration alarm is issued in step S15. In this way, if the flame detector 7a is normal, the abnormal concentration alarm is issued and combustion is allowed to continue, thereby maintaining combustion efficiency.

Furthermore, even during combustion operation after the ignition timing, if the carbon monoxide concentration in the exhaust gas is found to be an abnormal value, which could be the value that occurs when a misfire occurs, based on the detection results of the gas detection device 10 in step S22, the process proceeds to step S13. As a result, even after the ignition timing, the gas detection device 10 can be used to determine whether the detection by the flame detector 7a is an erroneous detection.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Below, we will explain modifications of the above-described embodiment that can be applied to the present invention.

In the above embodiment, an example was described in which the flame detector 7a detects the presence or absence of a flame in the pilot burner 8, but the burner to be detected is not limited to this, and the main burner 20 may be the target of detection, or both the pilot burner 8 and the main burner 20 may be the target of detection. In other words, the target for which the presence or absence of a flame is determined by the flame determination process is not limited to the pilot burner 8, but may also be the main burner 20, or both the pilot burner 8 and the main burner 20.

In the above embodiment, an example was described in which the target gas for detection by the gas detection device 10 was carbon monoxide in exhaust gas, but the target gas for detection is not limited to this and may be carbon dioxide, oxygen, nitrogen oxides, etc. Furthermore, as long as the gas detection device 10 can detect the concentration of gas after combustion, it may be installed in, for example, the boiler main body 2 and be able to detect the target gas within the boiler main body 2.

In the above embodiment, an example was described in which the light blocking device 7b was used in the flame determination process, but the light blocking device 7b may not be used. Specifically, if it is determined in step S12 of FIG. 2 that the carbon monoxide concentration in the exhaust gas does not exceed the predetermined threshold based on the detection result of the gas detection device 10, the process may proceed to step S16 and perform misfire control. Also, if it is determined in step S22 of FIG. 2 that the carbon monoxide concentration in the exhaust gas is an abnormal value based on the detection result of the gas detection device 10, the process may proceed to step S16 and perform misfire control.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications that are equivalent in meaning to and within the scope of the claims.

REFERENCE SIGNS LIST 1 Boiler 2 Boiler body 3 Blower 4 Flue 5 Fuel supply line 5a Fuel supply line 5b Fuel supply line 6 Control unit 7a Flame detector 7b Light blocking device 8 Pilot burner 9 Ignition device 10 Gas detection device 11 On-off valve 12 On-off valve 13 Fuel supply amount adjustment valve 14 On-off valve 15 On-off valve 20 Main burner 30 Air supply path 30a Pilot air supply path

Claims (3)

a burner that generates a flame;
an ignition device for igniting the burner;
a flame detection means for detecting the presence or absence of a flame in the burner;
a concentration detection means for detecting the concentration of a detection target gas contained in the gas after combustion by the flame;
a control means for performing a predetermined misfire control when it is determined that no flame is generated based on a comparison result between the concentration detected by the concentration detection means and a predetermined threshold value, even if the flame detection means detects the presence of a flame at the ignition timing when ignition processing for igniting the burner is performed ,
the flame detection means detects the presence or absence of a flame based on the presence or absence of incident light,
a light-blocking means that can be switched between a blocking state in which the light of the flame is blocked from entering the flame detection means and a non-blocking state in which the light of the flame is not blocked from entering the flame detection means;
and a determining means for determining whether or not a flame has been detected by the flame detecting means at the ignition timing by bringing the light blocking means into the blocking state when it is determined that no flame has been detected based on a comparison result between the concentration detected by the concentration detecting means and a predetermined threshold value,
The control means performs the misfire control when the determination means determines that the presence of a flame is still detected. The misfire control is a control for stopping a process for combustion,
2. The combustion device according to claim 1, wherein, when the determination means determines that no flame has been detected, the control means continues the combustion process while performing notification control to notify the user that it has been determined that no flame has been generated based on a comparison result between the concentration detected by the concentration detection means and a predetermined threshold value. 3. The combustion apparatus according to claim 1, wherein when the determination means determines that no flame has occurred based on a comparison result between the concentration detected by the concentration detection means and a specific value even after the ignition timing, the determination means sets the light blocking means to the blocking state to determine whether or not a flame has still been detected by the flame detection means.