Combustion equipment

Abstract

To provide a combustion apparatus capable of stably specifying wrong detection of flames due to deterioration of flame detection means on a long-term basis.SOLUTION: A combustion apparatus includes: a flame detector for detecting presence / absence of flames in a burner; and a gas detector detecting a concentration of detection target gas included in gas burned by flames. At ignition timing when ignition processing for igniting the burner is performed, even when presence of flames is detected by the flame detector, if determining that no flames are generated on the basis of a result of a comparison between the concentration detected by the gas detector and a predetermined threshold value, the combustion apparatus performs predetermined misfire time control.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a combustion device. [Background technology]

[0002] Combustion devices are equipped with flame detection means for detecting 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. One flame detection means uses an ultraviolet detector to detect the flame. Furthermore, when the ultraviolet detector deteriorates, it self-discharges, resulting in a false detection of a flame even when there is no flame. To identify such a false detection, 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 detection makes it possible to identify that the ultraviolet detector has deteriorated and therefore misdetected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 6-100332 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the shutter in the conventional combustion device is a physically operated device, and therefore, if the shutter operates more frequently, the life of the shutter mechanism is shortened accordingly.

[0005] The present invention has been devised in view of the above circumstances, and its object is to provide a combustion apparatus that can stably identify erroneous detection of a flame due to deterioration of the flame detection means for a long period of time. [Means for solving the problem]

[0006] 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 generated based on a result of comparing the concentration detected by the concentration detection means with a predetermined threshold value, even if the presence of a flame is detected by the flame detection means 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, and further includes a shading means that 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 that, 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.

[0007] According to the above configuration, since the concentration detection means does not physically operate, frequent detection of the concentration of the target gas does not have much effect on the life of the concentration detection means, and therefore, when the flame detection means detects the presence of a flame, it can be stably determined over the long term whether the detection is a false detection.

[0009] Also,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 a false 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 a false detection.

[0010] Preferably, the misfire control is a control that stops the process for combustion, and when the judgment means determines that no flame has been detected, the control means continues the process for combustion while performing notification control to notify that it has been determined that no flame has occurred based on the result of comparing the concentration detected by the concentration detection means with a predetermined threshold value.

[0011] According to the above configuration, when the judgment 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.

[0012] 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 shading means to the blocking state to determine whether or not a flame has still been detected by the flame detection means.

[0013] According to the above configuration, even after the ignition timing, it is possible to use the concentration detection means to determine whether the detection by the flame detection means is an erroneous detection. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram schematically illustrating the configuration of a boiler in which a combustion device is used. [Figure 2] 10 is a flowchart illustrating an example of a flame determination process. DETAILED DESCRIPTION OF THE INVENTION

[0015] The combustion device according to the present disclosure is a combustion device used in a boiler, 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 equivalent to the claims are intended to be included in the present invention.

[0016] <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.

[0017] 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 through an air supply path 30, a flue 4 that discharges exhaust gases and the like 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. Note that, although an example in which the fuel is gas will be described, the fuel is not limited to a gas such as gas, and may be a liquid such as oil.

[0018] The main burner 20 is provided 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 has its tip close to the main burner 20 and is provided so as to be able to ignite the main burner 20.

[0019] The fuel supply line 5 includes a fuel supply line 5a connected to an air supply passage 30 and a fuel supply line 5b branching off and connected to a pilot burner 8. The fuel supplied from the fuel supply line 5a to the air supply passage 30 is mixed with air blown from the blower 3 and supplied to the main burner 20 in the boiler main 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 a pilot air supply passage 30a branching off upstream from the air supply passage 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 amount adjustment valve 13. The fuel supply amount adjustment valve 13 functions as a pressure adjustment valve that can adjust the flow rate of fuel supplied to the boiler main body 2 and also has a shut-off function. The fuel supply amount 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 adjusting valve 13 is not limited to a motor valve as long as it adjusts the flow rate of fuel, and may be, for example, an air-operated control valve. Also, the fuel supply line 5b is provided with on-off valves (solenoid valves) 14 and 15 for opening and closing the flow path.

[0020] 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 to generate a flame, which ignites the main burner 20 and burns the fuel in the boiler body 2.

[0021] The flame detector 7a is positioned so as to be able to detect at least the presence or absence of a flame from the pilot burner 8. The flame detector 7 is a light detection means such as an ultraviolet photocell, a cadmium sulfide cell, or a lead sulfide cell, and detects the flame as light (including visible and invisible light). The flame detector 7 is preferably an ultraviolet detector such as an ultraviolet photocell that detects the presence or absence of a flame based on ultraviolet light, but is not limited to this and may also be a detector that detects visible light or infrared light. Among detectors, ultraviolet detectors are preferably used 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. Furthermore, compared to detectors that detect visible light or infrared light, they are less sensitive to the red heat of the furnace wall and have high accuracy in detecting blue flames.

[0022] The shading device 7b is provided between the position where the flame of the pilot burner 8 is generated and the flame detector 7a. While Fig. 1 shows an example in which the flame detector 7a is disposed at a predetermined distance from the shading device 7b, the flame detector 7a and the shading device 7b may be disposed close to each other, with the flame detector 7a disposed immediately before (for example, adjacent to) the shading device 7b (either an integrated type or a separate type may be used). The shading device 7b is composed of a shutter that is arranged so that its position can be changed between a blocking position (blocking state) in which the light of the flame of the pilot burner 8 is blocked from entering the flame detector 7a, and a non-blocking position (non-blocking state) in which the light of the flame is not blocked from entering the flame detector 7a, based on a control signal from the control unit 6.

[0023] Gas detection device 10 is provided at a predetermined position in flue 4. Gas detection device 10 is equipped with a gas sensor, and is configured to detect the exhaust gas extracted from flue 4 as a detection target gas using the gas sensor. Gas detection device 10 is also configured to return the exhaust gas extracted from flue 4 back to flue 4. The gas sensor shown here is one that detects the concentration of carbon monoxide contained in the extracted gas (exhaust gas).

[0024] The control unit 6 is realized by a computer including an internal memory, a timer, and an arithmetic processing unit. The control unit 6 adjusts the supply flow rate of fuel supplied from the fuel supply line 5a to the air supply passage 30 (and thus the main burner 20) based on the supply flow rate of combustion air to the boiler body 2 according to the stage of combustion. That is, if the flow rate of combustion air 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 flow rate of combustion air 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 it is not limited to this, and may 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 further has a flame determination function.

[0025] The flame determination function of the control unit 6 is a function of determining 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 result of the flame detector 7a.

[0026] Furthermore, when the control unit 6 detects the presence of a flame in the pilot burner 8 through the first-stage determination, the control unit 6 determines the presence or absence of a flame in the pilot burner 8 through whether the concentration detected by the gas detection device 10 is a specific concentration that can be assumed when a flame is present, as a second stage. It has been confirmed that the concentration of carbon monoxide in the exhaust gas instantaneously exceeds a predetermined threshold value when the pilot burner 8 actually ignites, for example, and that it reaches an abnormal value (specific value) when a flame goes out during combustion operation. In light of this phenomenon, as a second stage separate from the first-stage determination, the control unit 6 determines the presence or absence of a flame in the pilot burner 8 by using the gas detection device 10 to compare the concentration of the gas to be detected (e.g., carbon monoxide) in the exhaust gas with a predetermined threshold value, an abnormal value, or the like.

[0027] Furthermore, when the second-stage determination does not detect the presence of a flame in the pilot burner 8, that is, when there is a discrepancy between the first-stage determination result and the second-stage determination result, the control unit 6 operates the shutter to put the light blocking device 7b into a light-blocking state as a third stage, and determines whether the detection result of the flame detector 7a still detects the presence of a flame in the pilot burner 8, that is, whether the flame detector 7a has made an erroneous detection. In this way, it is possible to determine whether the flame detector 7a has made an erroneous detection, etc.

[0028] The control unit 6 determines whether or not to supply fuel to the main burner 20 based on the determination result of the flame determination function. That is, the presence or absence of a flame is monitored by the flame determination function, and when it determines that a flame is occurring in the pilot burner 8 at the time of ignition, for example, the control unit 6 starts fuel supply to the main burner 20 and starts combustion by the combustion device. This makes it possible to prevent fuel supply from being started even when no flame is occurring in the pilot burner 8 due to erroneous detection by the flame detector 7a.

[0029] <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 for explaining an example of the flame determination process. The flame determination process is repeatedly executed by the control unit 6 at predetermined time intervals (for example, every second). In step S10, it is determined whether it is the ignition timing to perform ignition processing for igniting a burner (for example, 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 it has been determined that there is a flame based on the detection result by the flame detector 7a, as a first stage of determination. If it is not determined that there is a flame in step S11, it is highly likely that there is no ignition because the processes of steps S20 to S24 described below have been performed, and therefore misfire control (for example, not starting combustion or stopping combustion) is performed in step S16.

[0030] On the other hand, if it is determined in step S11 that a flame is present, then in step S12, as a second-stage determination, it is determined based on the detection result of 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 therefore the process proceeds to a third-stage determination. First, in step S13, light blocking device 7b is controlled to a blocked state. Next, in step S14, it is determined based on the detection result by flame detector 7a whether a flame is still present.

[0031] If it is not determined in step S14 that there is a flame, flame detector 7a has detected the absence of a flame in the shut-off state and is normal, but there is a possibility that an abnormal concentration alarm has been issued in gas detection apparatus 10, so a concentration abnormality alarm is issued in step S15. Note that even when a concentration abnormality alarm is issued, there is a high possibility that the concentration is a temporary abnormality due to an external factor, so the processing for combustion is continued and maintained. In contrast, if it is still determined that there is a flame in step S14, flame detector 7a has detected the presence of a flame even in the shut-off state and is abnormal, so misfire control is performed. Note that in this case, a flame detector abnormality alarm may be issued to indicate that an abnormality has occurred in flame detector 7a, as in step S24 described below.

[0032] Returning to step S10, if it is not determined that it is the timing for ignition, it is determined in step S20 whether or not combustion drive is already in progress (for example, a state in which the control unit 6 is controlling the on-off valves 14, 15 to be open). If it is determined in step S20 that combustion drive is in progress, it is determined in step S21 whether or not it has been determined that there is a flame, based on the detection result by the flame detector 7a. If it is not determined that there is a flame in step S21, there is a high possibility that a misfire has occurred, and therefore misfire control is performed in step S16.

[0033] On the other hand, if it is determined in step S21 that a flame is present, it is determined in step S22 based on the detection result of gas detection device 10 whether the carbon monoxide concentration in the exhaust gas is an abnormal value that can be assumed when a fire has occurred. If it is not determined in step S22 that the concentration is an abnormal value, the determination result in step S21 and the determination result in step S22 are consistent, and the flame determination process is terminated. In contrast, if it is determined in step S22 that the concentration is an abnormal value, there is a discrepancy between the determination result in step S21 and the determination result in step S22, and therefore the process proceeds to step S13 to perform a determination using light blocking device 7b.

[0034] When it is not determined in step S20 that combustion is being driven, that is, when combustion is stopped and it is neither ignition timing nor combustion is being driven, and under circumstances where it would not normally be determined that a flame is present, it is determined in step S23 based on the detection result by flame detector 7a whether or not a flame is present. If it is not determined that a flame is present in step S23, flame detector 7a is normal, and the flame determination process is terminated. On the other hand, if it is determined that a flame is present in step S23, it is clear that an abnormality has occurred in flame detector 7a, and therefore a flame detector abnormality alarm is issued in step S24 to indicate that an abnormality has occurred in flame detector 7a, regardless of the detection result of gas detection device 10.

[0035] In boiler 1 equipped with the combustion device according to this embodiment, at the timing of ignition, it is determined in step S11 of FIG. 2 that a flame is present based on the detection result by flame detector 7a. Then, in step S12, it is determined that a flame is not present based on the detection result by gas detection device 10 because the concentration does not exceed a predetermined threshold. As a result, in step S13, light blocking device 7b is controlled to a shutoff state. When it is determined in step S14 that a flame is still present based on the detection result by flame detector 7a, an abnormality in flame detector 7a is assumed, and misfire control is performed in step S16. Because gas detection device 10 does not physically operate, frequent detection of the concentration of carbon monoxide in the exhaust gas, which is the target gas, has little effect on the life of gas detection device 10. Meanwhile, the frequency with which light blocking device 7b is controlled to a shutoff state can be reduced. As a result, when a flame is detected by flame detector 7a, it is possible to stably determine whether the detection is a false positive over the long term.

[0036] Furthermore, if it is not determined in step S14 that a flame is present based on the detection result by flame detector 7a, the process for combustion continues, and an abnormal concentration alarm is issued in step S15. In this way, if flame detector 7a is normal, the abnormal concentration alarm is issued and combustion is continued, thereby maintaining combustion efficiency.

[0037] Furthermore, even during combustion operation after the ignition timing, if the carbon monoxide concentration in the exhaust gas is an abnormal value that can be obtained when a misfire occurs based on the detection result of gas detection device 10 in step S22, the process proceeds to step S13. As a result, even after the ignition timing, it is possible to use gas detection device 10 to determine whether the detection by flame detector 7a is an erroneous detection.

[0038] The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Modifications of the above-described embodiment that can be applied to the present invention will be described below.

[0039] In the above embodiment, an example has been 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 detection target, or both the pilot burner 8 and the main burner 20 may be the detection target. 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 be the main burner 20, or both the pilot burner 8 and the main burner 20.

[0040] In the above embodiment, an example has been described in which the gas to be detected by gas detection device 10 is carbon monoxide in exhaust gas, but the gas to be detected is not limited to this and may be any of carbon dioxide, oxygen, nitrogen oxides, etc. Furthermore, gas detection device 10 may be provided in boiler main body 2, for example, and may be capable of detecting the target gas within boiler main body 2, as long as it can detect the concentration of gas after combustion.

[0041] In the above embodiment, an example in which light blocking device 7b is used in the flame determination process has been described, but light blocking device 7b may not be used. Specifically, when it is determined in step S12 of Fig. 2 based on the detection result of gas detection device 10 that the carbon monoxide concentration in the exhaust gas has not exceeded the predetermined threshold, the process may proceed to step S16 to perform misfire control. Also, when it is determined in step S22 of Fig. 2 based on the detection result of gas detection device 10 that the carbon monoxide concentration in the exhaust gas is an abnormal value, the process may proceed to step S16 to perform misfire control.

[0042] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0043] 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 Shading device 8 Pilot Burner 9 Ignition device 10 Gas detection equipment 11 On-off valve 12 On-off valve 13 Fuel supply adjustment valve 14 On-off valve 15 On-off valve 20 Main Burner 30 Air supply line 30a Pilot air supply line

Claims

1. 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.

2. 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. 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.

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