Boiler

Abstract

To provide a boiler capable of continuing control to keep oxygen concentration in an exhaust gas constant as long as possible.SOLUTION: In order to keep a flow rate according to a combustion amount in a boiler, combustion air is supplied, a flow rate of the supplied combustion air is detected, a correction value is specified to keep an air ratio within a prescribed range, a flow rate of a fuel to be supplied is adjusted on the basis of the specified correction value and the detected flow rate of the combustion air, and the adjustment based on the correction value is not performed when an abnormality condition is established due to a variation of the correction value exceeding a specific amount.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, there have been boilers equipped with combustion devices that perform multi-position control (high combustion, medium combustion, low combustion, etc.) and proportional control by providing an adjustment valve on a fuel supply line that supplies fuel to a nozzle or other ejection section, and controlling a proportional valve (adjusting valve) in conjunction with the flow rate of combustion air to adjust the flow rate of fuel. Also, as such boilers, there have been those that adjust the flow rate of fuel according to the flow rate of the supplied combustion air (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-2787 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned boilers, for example, it is desirable to keep the oxygen concentration of the exhaust gas (or the air ratio during combustion, etc.) constant, but in reality, the oxygen concentration of the exhaust gas fluctuates depending on external factors (for example, the temperature of the fuel, the temperature of the combustion air, the composition of the fuel, etc.), which may result in combustion abnormalities such as misfires and increases in carbon monoxide. Similar problems may also occur in boilers that adjust the flow rate of the combustion air depending on the flow rate of the supplied fuel.

[0005] The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a boiler that can maintain, as long as possible, the control for keeping the oxygen concentration in the exhaust gas constant. [Means for solving the problem]

[0006] In order to achieve the above object, a boiler according to one aspect of the present invention includes supply means for supplying combustion air or fuel so that the flow rate corresponds to an amount of combustion, flow rate detection means for detecting the flow rate of the combustion air or the flow rate of the fuel supplied, correction value specifying means for specifying a correction value for bringing the air ratio into a predetermined range, and flow rate adjustment means for adjusting the flow rate of the fuel supplied or the flow rate of the combustion air supplied, based on the correction value specified by the correction value specifying means and the flow rate of the combustion air detected by the flow rate detection means or the flow rate of the fuel detected by the flow rate detection means, and when an abnormal condition is established by the amount of change in the correction value exceeding a specific amount, the flow rate adjustment means does not perform adjustment based on the correction value. First, the change amount of the correction value is the change amount between the correction value before the control for changing the combustion amount is started and the correction value after the flow rate of the combustion air or fuel supplied by the supply means becomes a flow rate corresponding to the changed combustion amount. .

[0007] According to the above configuration, the flow rate of the fuel or the flow rate of the combustion air is adjusted based on the correction value, so that the air ratio falls within a predetermined range and the oxygen concentration in the exhaust gas can be kept constant. On the other hand, if the flow rate is adjusted based on a correction value that has changed rapidly beyond a threshold value, there is a risk of causing combustion abnormalities such as misfires and increased carbon monoxide. However, when the change in the correction value exceeds a specific amount and an abnormal condition is established, the adjustment based on the correction value is not performed. As a result, compared to when an abnormality is determined based on the difference from a fixed value, for example, the adjustment of the flow rate based on the correction value can be continued when the change in the correction value does not exceed a specific amount, so that the adjustment of the flow rate based on the correction value can be maintained as long as possible within a range that does not cause combustion abnormalities (a stricter range). In addition, when there is a change in the combustion amount, which is likely to cause a large change in the correction value, the correction value during the change in the combustion amount is not taken into account, and an abnormality is determined based on the change in the correction value before the change in the combustion amount and the correction value after the change in the combustion amount, thereby improving the accuracy of the abnormality determination.

[0008] Preferably, the abnormal condition is established when an amount of change in the correction value specified by the correction value specifying means from an average value for a predetermined period of time exceeds the specified amount.

[0009] According to the above configuration, even if an abnormality is determined based on the amount of change from the correction value at a certain timing (moment), an abnormality may not be determined because an abnormality is determined more strictly based on an averaged value using more correction values ​​when the abnormality is determined based on the amount of change from the average value over a predetermined period. As a result, the flow rate adjustment based on the correction value can be maintained as long as possible within a range (stricter range) that does not cause combustion abnormality.

[0010] Preferably, the end point of the predetermined period is set to a timing that is a certain time before the current time.

[0011] According to the above configuration, an abnormality is determined based on the amount of change from the average value for a predetermined period up to a certain time ago without taking into account the correction value immediately before the current time, thereby improving the accuracy of the abnormality determination. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram illustrating a schematic configuration of a boiler. [Diagram 2] 4 is a flowchart illustrating an example of control of a boiler. [Diagram 3] FIG. 11 is a diagram illustrating an example of a predetermined period that ends a certain time before the current time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Overview of the configuration> A boiler 1 according to an embodiment of the present invention will be described below with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration of a boiler 1 according to an embodiment of the present invention.

[0016] The boiler 1 includes a boiler body 2 that burns fuel to generate steam, a blower (blower means) 3 that sends air into the boiler body 2 via an air supply passage 30, a flue 4 that guides exhaust gas and the like from the boiler body 2, and a fuel supply line (fuel supply passage) 5 that supplies fuel to the boiler body 2. 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.

[0017] The fuel supply line 5 is connected to an air supply passage 30. The fuel supplied from the fuel supply line 5 is mixed with air blown from the blower 3 in the air supply passage 30, and is supplied to the burner 20 in the boiler body 2.

[0018] The air supplied from the blower 3 is supplied as combustion air to the burner 20 in the boiler body 2 via the air supply passage 30. The flow rate of the combustion air is adjusted by providing a damper 7 in the air supply passage 30 and adjusting the position (opening) of the damper 7, or alternatively or in addition, by using an inverter to change the rotation speed of the fan of the blower 3. In this embodiment, the flow rate of the combustion air is adjusted by controlling the opening of the damper 7 and the inverter control of the blower 3.

[0019] The fuel supply line 5 is provided with on-off valves (solenoid valves) 11, 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 capable of adjusting the flow rate of fuel supplied to the boiler body 2, and also has a shutoff function. The fuel supply amount adjustment valve 13 is provided downstream of the on-off valves 11, 12, and is a motor valve whose opening is adjusted by the control device 6. Note that the fuel supply amount adjustment 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-type control valve.

[0020] The control device 6 is realized by a computer including an internal memory, a timer, and an arithmetic processing unit, and controls the fuel supply amount adjusting valve 13, the blower 3, and the damper 7 based on signals from each sensor that is electrically connected to it.

[0021] In the air supply passage 30 in this embodiment, a combustion air decompression member 8 such as a punched metal is provided downstream of the damper 7. The air flow detection unit 9 is equipped with a differential pressure sensor that detects the differential pressure before and after the combustion air decompression member 8, and outputs differential pressure information that can identify the detected differential pressure. The air flow detection unit 9 is electrically connected to the control device 6. This allows the differential pressure information from the air flow detection unit 9 to be input to the control device 6. The analog signal output from the air flow detection unit 9 is converted to a digital signal and input to the control device 6.

[0022] The control device 6 controls the combustion stage to one of a plurality of types of combustion stages with different combustion amounts, for example, a low combustion stage L, a medium combustion stage M, or a high combustion stage H. The control device 6 controls the combustion stage according to a set target steam pressure and the steam pressure of the steam header. The control device 6 controls the blower 3 so as to have a configuration (e.g., rotation speed, frequency) according to the controlled combustion stage, and supplies an amount of combustion air according to the combustion stage. The control device 6 calculates (detects) the flow rate of combustion air actually supplied to the boiler body 2 based on the differential pressure information detected by the air flow detection unit 9.

[0023] The control device 6 adjusts the aperture of the fuel supply amount adjustment valve 13 based on the calculated flow rate of the combustion air and a correction value described later. For example, if the flow rate of the combustion air increases, the aperture of the fuel supply amount adjustment valve 13 is increased to increase the flow rate of fuel, whereas if the flow rate of the combustion air decreases, the aperture of the fuel supply amount adjustment valve 13 is decreased to decrease the flow rate of fuel.

[0024] The control device 6 includes a control unit 61 and a storage unit 62. The control unit 61 transmits an opening degree specifying signal for specifying an opening degree to the fuel supply amount adjusting valve 13 based on the opening degree adjustment information stored in advance in the storage unit 62. As a result, the fuel supply amount adjusting valve 13 is controlled to an opening degree according to the differential pressure before and after the combustion air pressure reducing member 8, and can adjust the flow rate of the fuel supplied to the boiler body 2. Note that the opening degree adjustment information may be, for example, a table capable of specifying the opening degree of the fuel supply amount adjusting valve 13 according to the differential pressure (or the flow rate of the combustion air calculated from the differential pressure), or may be an arithmetic expression for specifying the opening degree of the fuel supply amount adjusting valve 13 according to the differential pressure (or the flow rate of the combustion air calculated from the differential pressure).

[0025] The storage unit 62 stores various information related to the boiler 1, and in this embodiment, a correction value for correcting the fuel supply flow rate is stored. The opening degree of the fuel supply amount adjustment valve 13 is specified according to the opening degree adjustment information based on the pressure difference before and after the combustion air pressure reducing member 8. Therefore, theoretically, the air ratio based on the flow rate of the combustion air and the flow rate of the fuel supplied will converge to an air ratio corresponding to the combustion stage (combustion amount). However, for example, due to external factors (e.g., the temperature of the fuel, the temperature of the combustion air, the composition of the fuel, etc.), there may actually be cases where the air ratio does not converge to an air ratio corresponding to the combustion stage. The correction value is a value for correcting the amount of fuel supply to converge to an air ratio corresponding to the combustion stage (or within a predetermined range of the air ratio), and is updated as needed according to the value of a specific parameter (e.g., oxygen concentration of exhaust gas, etc.) that can be detected during the operating state. The correction value is updated by specifying as needed a correction value by feedback control or the like to converge (toward) an air ratio corresponding to the combustion stage being controlled (or within a predetermined range of the air ratio) according to the latest value of the specific parameter.

[0026] The boiler 1 of this embodiment detects, for example, the oxygen concentration of the exhaust gas as a specific parameter from time to time during operation. Based on the detected oxygen concentration of the exhaust gas and a predetermined reference oxygen concentration, for example, when the oxygen concentration of the exhaust gas is greater than the reference oxygen concentration, the control device 6 specifies a value (for example, a value greater than 1) for increasing the amount of fuel supplied since a high air ratio is established as the correction value, and stores the correction value in the storage unit 62, and when the oxygen concentration of the exhaust gas is less than the reference oxygen concentration, the control device 6 specifies a value (for example, a value less than 1) for decreasing the amount of fuel supplied since a low air ratio is established as the correction value, and stores the correction value in the storage unit 62. In this way, the control device 6 repeatedly performs the process of specifying and storing the correction value during operation.

[0027] The control device 6 performs a process for correcting the opening of the fuel supply amount adjustment valve 13 specified according to the opening amount adjustment information based on the pressure difference before and after the combustion air pressure reducing member 8, using the most recent correction value. For example, when the correction value is a value larger than 1, the opening is corrected to a larger opening (opening at which the flow rate increases) than the opening of the fuel supply amount adjustment valve 13 specified according to the opening amount adjustment information, and when the correction value is a value smaller than 1, the opening is corrected to a smaller opening (opening at which the flow rate decreases) than the opening of the fuel supply amount adjustment valve 13 specified according to the opening amount adjustment information. Thereby, when the engine is in an operating state in a certain combustion stage, the air ratio can be converged (closed) to an air ratio (or within a predetermined range of the air ratio) corresponding to the combustion stage, taking into account external factors. As a result, the air ratio falls within the predetermined range, and the oxygen concentration in the exhaust gas can be kept constant.

[0028] In addition, when the boiler transitions between combustion stages (when the combustion amount changes), a process is performed to adjust the supply flow rate of the combustion air to the boiler body 2 to a flow rate corresponding to the combustion stage after the transition, and then a process is performed to adjust the supply flow rate of the fuel according to the actual supply flow rate of the combustion air. In such a transition between combustion stages of the boiler, the correction value fluctuates greatly. For example, when transitioning to a combustion stage with a large combustion amount, such as when transitioning from the low combustion stage L to the medium combustion stage M, the supply flow rate of the combustion air tends to be excessive relative to the supply flow rate of the fuel, resulting in a high air ratio. For this reason, the correction value can fluctuate greatly to a value that increases the supply flow rate of the fuel to converge the air ratio. On the other hand, when transitioning to a combustion stage with a small combustion amount, such as when transitioning from the medium combustion stage M to the low combustion stage L, the supply flow rate of the combustion air tends to be excessive relative to the supply flow rate of the fuel, resulting in a low air ratio. For this reason, the correction value can fluctuate greatly to a value that reduces the supply flow rate of the fuel to converge the air ratio. However, if the change in the correction value is too large (not limited to when the combustion amount changes), it may cause combustion abnormalities such as misfires or an increase in carbon monoxide.

[0029] In order to suppress such a problem, for example, it may be assumed that a combustion abnormality occurs when the correction value at the current time exceeds a predetermined range (for example, ±0.15) based on a certain value (for example, 1) (when the correction value is less than 0.85 or exceeds 1.15), and the opening degree of the fuel supply amount adjustment valve 13 is not corrected based on the correction value when the correction value at the current time exceeds the predetermined range. However, the main cause of combustion abnormality is when the amount of change between the correction value a certain time ago and the correction value at the current time changes suddenly and exceeds a specific amount. Therefore, even if the predetermined range based on a certain value is exceeded, combustion abnormality does not occur unless the amount of change between the correction value a certain time ago and the correction value at the current time exceeds a specific amount. As a result, if the flow rate adjustment based on the correction value is not performed when the correction value at the current time exceeds the predetermined range, the frequency of not adjusting the flow rate based on the correction value increases even in cases where adjustment based on the correction value would not cause combustion abnormality. Therefore, in the boiler 1 of this embodiment, when the amount of change between the correction value from a predetermined time ago and the correction value at the current time exceeds a specific amount, it is deemed that an abnormal condition has been established, and the opening degree of the fuel supply amount adjustment valve 13 is not corrected based on the correction value whose amount of change exceeds the specific amount, but the opening degree of the fuel supply amount adjustment valve 13 is adjusted based on the differential pressure information (differential pressure, flow rate of combustion air) detected by the air flow detection unit 9. Such control will be described in more detail below.

[0030] <Boiler control processing> 2 is a flow chart for explaining an example of boiler control according to the present invention. The control device 6 performs this control at regular intervals (for example, 0.1 seconds) and continues to perform this control while the boiler 1 is in operation.

[0031] In step S01, it is determined whether or not a transition in the combustion stage (a change in the amount of combustion) is necessary based on the detected steam pressure in the steam header and the target steam pressure. If it is not determined in step S01 that a transition in the combustion stage is necessary, the process proceeds to step S04. On the other hand, if it is determined in step S01 that a transition in the combustion stage is necessary, the process proceeds to step S02.

[0032] In step S02, the combustion stage is shifted. In step S03, the blower 3 is controlled in a manner corresponding to the combustion stage shifted in step S02 (a manner in which the rotation speed or frequency corresponds to the combustion stage). In step S04, the air flow rate of the combustion air is detected (specified) based on the differential pressure detected by the air flow rate detection unit 9.

[0033] In step S05, a specific parameter that varies depending on the operating state of the boiler 1 is identified. The specific parameter is an index of a change (external factor) in the environment that causes a change in the amount of steam extracted. In this embodiment, the O2 concentration of the exhaust gas from the boiler main body 2 is used as the specific parameter. 2 The oxygen concentration in the exhaust gas detected by the sensor is used. 2 The sensor is provided at a predetermined position in the flue 4. In step S06, a correction value for bringing the air ratio into a predetermined range is specified based on the specific parameters specified in step S05, and stored in the memory unit 62. Note that the correction value is usually specified to be within a range of, for example, 0.3 to 1.7, but is not limited thereto. In step S07, an average value of the correction values ​​for a predetermined period ending a certain time before the current time (hereinafter also referred to as an average correction value) is calculated. In the memory unit 62, a history of the correction values ​​for the predetermined period is stored together with the time, etc., so that the average correction value for the predetermined period can be calculated. The certain period refers to the period during which the exhaust gas generated by the combustion in the burner 20 is mixed with the O2 gas in the flue 4. 2Any time longer than the time required for the combustion amount to reach the sensor may be used, and in this embodiment, the time is set to be longer than the average time required from the start of a change in the combustion amount (for example, a change in the rotation speed of the blower 3) to its completion (for example, the rotation speed of the blower 3 reaches a rotation speed corresponding to the combustion amount after the change), for example 5 seconds, but not limited to this. The predetermined period is a period that ends a certain amount of time ago, for example 3 seconds, but not limited to this.

[0034] In step S08, it is determined whether the difference between the correction value specified at the current time (the most recent correction value specified and stored in step S06, hereinafter also referred to as the current correction value) and the average correction value calculated in step S07 is within a specific amount. The specific amount is a value that is confirmed and set by a prior investigation or the like as a change amount in the correction value that may cause combustion abnormalities such as misfire or an increase in carbon monoxide, and is, for example, 0.3, but is not limited to this and may be any value between 0.1 and 1.

[0035] Here, the fixed time and the predetermined period will be described. FIG. 3 is a diagram for explaining an example of a predetermined period ending a fixed time before the current time. In FIG. 3, the vertical axis shows an example of transition of the combustion stage, the rotation speed of the blower, and the correction value, and the horizontal axis shows the flow of time. In the low combustion stage L, the rotation speed of the blower 3 is controlled to the rotation speed for low combustion in step S03 of FIG. 2. FIG. 3 shows how the value of the correction value specified in step S06 of FIG. 2 fluctuates around the value a in the low combustion stage L.

[0036] Timing A in Fig. 3 illustrates a certain timing during control in the low combustion stage L. At timing A, an average correction value for a predetermined period for time A, which ends a certain time before timing A, is calculated in step S07, and it is determined in step S08 whether the difference between the current correction value at timing A and the calculated average correction value is within a specific amount. Note that when the combustion stage (amount of combustion) is not changing, the correction value fluctuates near a predetermined value as shown in Fig. 3, and it is highly likely that it is determined to be within the specific amount unless a significantly influential external factor occurs.

[0037] On the other hand, when the combustion stage (combustion amount) changes, the correction value is likely to fluctuate significantly as described above. Timing B in FIG. 3 illustrates the timing when the transition from the low combustion stage L to the high combustion stage H is completed as an example of a case where the combustion amount changes. The timing when the transition to the high combustion stage H is completed refers to, for example, the timing when the rotation speed of the blower 3 is controlled to the rotation speed for high combustion and the flow rate of the combustion air supplied to the boiler body 2 becomes the flow rate of the high combustion stage H, as shown in FIG. 3, but is not limited to this as long as it is after that timing. In addition, as the rotation speed of the blower 3 changes after the combustion amount starts to change and the flow rate of the combustion air also changes, the correction value also fluctuates so as to obtain an appropriate air ratio, as shown in FIG. 3.

[0038] At the time B, in step S07, an average correction value for a predetermined period for time B, which ends at a certain time before the time B, is calculated, and in step S08, it is determined whether or not the difference between the current correction value at the time B and the calculated average correction value is within a specific amount. The certain time is set to be longer than the average time required from the start of the change in the combustion amount to its completion. For this reason, as shown in FIG. 3, the predetermined period for time B is the period up to the time before the change in the combustion amount starts, and in step S08 at the time B, it is determined whether or not the change in the correction value before the start of the control to change the combustion amount and the correction value after the flow rate of the combustion air supplied by the blower 3 becomes a flow rate corresponding to the changed combustion amount is within a specific amount. More specifically, it is determined whether or not the change in the correction value in the combustion stage before the start of the transition (for example, the low combustion stage L) and the correction value in the combustion stage after the transition is completed (for example, the high combustion stage H) is within a specific amount. 3 shows that the correction value specified in step S06 in FIG. 2 fluctuates around the value b (<value a) in the high combustion stage H. Also, while FIG. 3 shows an example in which the correction value decreases when the combustion amount increases, the correction value may increase when the combustion amount increases due to the usage environment or external factors, and the correction value may increase or decrease when the combustion amount decreases.

[0039] 2, if it is determined in step S08 that the difference is within the specific amount, the process proceeds to step S09. On the other hand, if it is not determined that the difference is within the specific amount, the process proceeds to step S10.

[0040] In step S09, the opening degree of the fuel supply amount regulating valve 13 is controlled based on the air flow rate detected in step S04 and the correction value updated and stored in step S06. That is, the opening degree of the fuel supply amount regulating valve 13 is corrected based on the correction value. This makes it possible to adjust the amount of fuel supply so as to converge to an air ratio (or within a predetermined range of the air ratio) corresponding to a certain combustion stage based on the value of a specific parameter during an operating state in that combustion stage.

[0041] On the other hand, if the change in the correction value is an amount of change that would cause a combustion abnormality, an abnormality is notified in step S10 (for example, a warning display, an alarm sound output, etc.), and in step S11, the opening of the fuel supply amount adjustment valve 13 is controlled based on the air flow rate detected in step S04, and the opening correction of the fuel supply amount adjustment valve 13 based on the correction value is not performed.

[0042] As described above, in this embodiment, as shown in steps S08 to S11 in FIG. 2, if it is determined that the difference between the current correction value specified and stored in step S06 in FIG. 2 and the average correction value calculated in step S07 in FIG. 2 is within a specific amount, the opening degree of the fuel supply amount adjustment valve 13 is controlled based on the air flow rate detected in step S04 in FIG. 2 and the correction value updated and stored in step S06 in FIG. 2, as shown in step S09 in FIG. 2. Therefore, the flow rate of the combustion air to be supplied is adjusted based on the correction value, so that the air ratio is within a predetermined range and the oxygen concentration in the exhaust gas can be kept constant. On the other hand, if it is not determined that the difference between the current correction value specified and stored in step S06 in FIG. 2 and the average correction value calculated in step S07 in FIG. 2 is within a specific amount, the opening degree of the fuel supply amount adjustment valve 13 is controlled based on the air flow rate detected in step S04, as shown in step S11 in FIG. 2, and the opening degree correction of the fuel supply amount adjustment valve 13 based on the correction value is not performed. Therefore, if the flow rate is adjusted based on a correction value that has changed rapidly beyond a threshold value, there is a risk of causing combustion abnormalities such as misfires and increased carbon monoxide. If an abnormality is determined based on whether the correction value at the current time exceeds a predetermined range (for example, ±0.15) based on a constant value (for example, 1) (when the correction value is less than 0.85 or exceeds 1.15), the determination standard is a constant value, and as a result, even when a combustion abnormality would not occur, it is determined to be abnormal, increasing the frequency with which adjustment based on the correction value cannot be performed. On the other hand, in the boiler 1 of this embodiment, the correction values ​​that change each time are compared, and when the change amount of the correction value does not exceed a specific amount, the flow rate adjustment based on the correction value can be continued as much as possible within a range (stricter range) that does not cause combustion abnormalities.

[0043] In this embodiment, as shown in step S07 of FIG. 2 and FIG. 3, the change amount of the correction value is determined as the difference between the current correction value (near the value a, determined in step S06) and the average correction value (near the value a, calculated in step S07) in the predetermined period for time A at timing A, and is determined as the difference between the current correction value (near the value b, determined in step S06) and the average correction value (near the value a, calculated in step S07) in the predetermined period for time B at timing B. For this reason, even if an abnormality is determined based on the correction value at a certain timing (moment) in the predetermined period for time A or the correction value at a certain timing (moment) in the predetermined period for time B, if an abnormality is determined based on the change amount from the average value in the predetermined period, the abnormality may not be determined as an abnormality because the abnormality is determined more strictly based on the averaged value using more correction values. As a result, the flow rate adjustment based on the correction value can be maintained as long as possible within a range (stricter range) in which combustion abnormality does not occur.

[0044] In this embodiment, the end point of the predetermined period is set for each of timings A and B, and is a certain time (for example, 5 seconds) before each timing, as shown in step S07 in Fig. 2 and Fig. 3. In this way, since an abnormality is determined based on the amount of change from the average value in the predetermined period up to the certain time ago without considering the correction value immediately before the current time, the accuracy of the abnormality determination can be improved.

[0045] Furthermore, in this embodiment, as shown in step S07 of FIG. 2 and in FIG. 3, the amount of change in the correction value at timing B is the difference (for example, ≒ numerical value a - numerical value b) between the average correction value in the low combustion stage (near numerical value a) and the current correction value in the high combustion stage (near numerical value b). Therefore, when there is a change in the combustion amount which is likely to cause a large amount of change in the correction value, the correction value during the change in the combustion amount is not taken into account, but an abnormality is determined based on the amount of change between the correction value before the change in the combustion amount and the correction value after the change in the combustion amount, thereby improving the accuracy of the abnormality determination.

[0046] 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.

[0047] In the above embodiment, an example was described in which the air ratio is adjusted by controlling the blower 3 in a manner corresponding to the combustion stage, detecting the air flow rate (combustion air supply flow rate) based on the differential pressure as shown in step S04 of FIG. 2, and then controlling the opening degree of the fuel supply amount adjustment valve 13 (fuel supply flow rate) based on the air flow rate and the correction value as shown in step S09. However, the process for adjusting the air ratio is not limited to this, and for example, the air ratio may be adjusted by controlling the opening degree of the fuel supply amount adjustment valve 13 so as to have an opening degree corresponding to the combustion stage, detecting the actual fuel supply flow rate, and controlling the air flow rate (combustion air supply flow rate, for example, the blower 3) based on the fuel supply flow rate and the correction value. When detecting the actual fuel supply flow rate, for example, orifices or the like may be provided at multiple locations in the fuel supply line 5 to detect the differential pressure, and the fuel supply flow rate may be detected based on the differential pressure. The correction value in this case is not a value for correcting the fuel supply flow rate, but a value for correcting the air flow rate (combustion air supply flow rate). Specifically, the control device 6 specifies and stores a correction value for reducing the air flow rate (for example, a value less than 1) based on the detected oxygen concentration of the exhaust gas and a predetermined reference oxygen concentration, for example, when the oxygen concentration of the exhaust gas is greater than the reference oxygen concentration, the air ratio is high, and specifies and stores a correction value for increasing the air flow rate (for example, a value greater than 1) based on the air ratio is low when the oxygen concentration of the exhaust gas is less than the reference oxygen concentration. In addition, the control device 6 performs a process for correcting the state (for example, the rotation speed) of the blower 3 specified based on the fuel supply flow rate using the correction value updated from time to time. Even in this configuration, if it is not determined that the difference between the current correction value specified and stored in step S06 of FIG. 2 and the average correction value calculated in step S07 of FIG. 2 is within a specific amount, it is determined that an abnormal condition is established, and the air flow rate is not adjusted based on the correction value. This makes it possible to prevent combustion abnormalities such as misfires and increased carbon monoxide.Furthermore, compared to judging an abnormality based on a difference from a constant value (for example, 1, which is the intermediate value when the possible correction values ​​are 0.3 to 1.7), for example, whether the difference between 1 and the current correction value is within a specific amount, the flow rate adjustment based on the correction value can be continued when the amount of change in the correction value does not exceed a specific amount, so that the flow rate adjustment based on the correction value can be maintained as long as possible within a range that does not cause a combustion abnormality (a stricter range). Note that, in the above example, an example of adjusting the mode (rotation speed, etc.) of the blower 3 has been shown as a method for controlling the air flow rate based on the correction value, but the present invention is not limited to this, and the opening of the damper 7 may be adjusted, or both the mode (rotation speed, etc.) of the blower 3 and the opening of the damper 7 may be adjusted.

[0048] In the above embodiment, when it is not determined that the change amount of the correction value is within the specific amount, an example is described in which the correction (adjustment) based on the correction value is not performed as illustrated in step S11. However, it is sufficient if the correction (adjustment) based on the current correction value that is not determined to be within the specific amount is not performed. For example, in step S11, control may be performed based on the air flow rate (differential pressure) and a value that causes the change amount of the correction value to be within the specific amount and is closest to the current correction value, that is, a correction (adjustment) based on a value that causes the change amount of the correction value to be within the specific amount and is closest to the current correction value may be performed. Note that the correction of the flow rate of the combustion air (or the flow rate of the fuel) is not limited to being performed based on the correction value, and may be performed instead or in addition to this based on the usage environment, situation, etc. during the operating state. For example, the opening degree of the fuel supply amount adjustment valve 13 may be corrected (adjusted) by taking into account the temperature of the fuel and the temperature of the combustion air, etc.

[0049] In the above embodiment, the specific parameters that vary depending on the operating state of the boiler 1 include the O2 of the exhaust gas from the boiler body 2, 2 Although an example has been described in which the oxygen concentration of the exhaust gas detected by a sensor is used, the present invention is not limited to this, and for example, directly measured values ​​of the exhaust gas temperature, air temperature, and heat generation amount may be used.

[0050] In the above embodiment, an example has been described in which the correction value is updated based on the detected oxygen concentration of the exhaust gas and the reference oxygen concentration. However, the present invention is not limited to this. For example, the correction value may be updated based on the calorific value of the fuel and the reference calorific value, or the mass flow rate of the fuel and the reference mass flow rate.

[0051] In the above embodiment, an example has been described in which the certain period is set to be longer than the average time required from the start of a change in the combustion amount (for example, a change in the rotation speed of the blower 3) until it is completed (for example, the rotation speed of the blower 3 reaches a rotation speed corresponding to the combustion amount after the change), and whether or not to perform adjustment based on a correction value is determined based on the amount of change between the correction value before the change in the combustion amount (or average correction value) and the correction value after the change in the combustion amount (current correction value). However, as described above, the certain period is set to be longer than the average time required from the start of a change in the combustion amount (for example, a change in the rotation speed of the blower 3) until it is completed (for example, the rotation speed of the blower 3 reaches a rotation speed corresponding to the combustion amount after the change). 2 It is sufficient that the time is equal to or longer than the time required for the combustion amount to reach the sensor. Even in this case, when changing the combustion amount, whether or not to perform adjustment based on the correction value may be determined based on the amount of change between the correction value (or average correction value) before the combustion amount change (before the transition starts, or a predetermined time before the transition start timing) and the correction value (current correction value) after the combustion amount change (after the transition is completed), regardless of the fixed time. Since the correction value fluctuates relatively greatly before and after the change in the combustion amount, it is effective to determine whether the amount of change in the correction value at that time exceeds a specific amount.

[0052] In the above embodiment, an example was described in which the difference between the correction value (current correction value) specified at the current time specified in step S06 in FIG. 2 and the average correction value (average correction value) in a predetermined period calculated in step S07 is used as the change amount of the correction value. That is, an example was described in which the instantaneous value of the current time is used as the correction value to be judged, and the average correction value in a predetermined period before the current time is used as the correction value to be judged. However, the correction value to be judged may be the average correction value in a period from a predetermined time ago (for example, 3 seconds ago) to the current time, as long as the correction value of the current time is taken into consideration. Also, the correction value to be judged may be the correction value (instantaneous value) a certain time ago before the current time. That is, the change amount of the correction value is not limited to the one specified by using the instantaneous value of the current time as the correction value to be judged and the average correction value in a predetermined period before the current time as the correction value to be judged as in the above embodiment, but may be the following. Example 1: The correction value to be judged is the average correction value for the period from a specified time ago (e.g., 3 seconds ago) to the current time, and the correction value to be used as the judgment criterion is the average correction value for a specified period prior to the current time. Example 2: The instantaneous value at the current time is used as the correction value to be judged, and the correction value (instantaneous value) from a certain time before the current time is used as the judgment criterion. Example 3: The correction value to be judged is the average correction value from a certain time ago (for example, 3 seconds ago) to the current time, and the correction value to be used as the judgment criterion is determined using the correction value (instantaneous value) from a certain time ago before the current time.

[0053] In the above embodiment, an example was described in which if the amount of change in the correction value exceeds a specific amount, it is determined that an abnormal condition exists and the flow rate is not adjusted based on the correction value, but in addition to this, it is also possible to set upper and lower limit values ​​for the correction value (values ​​including 0.3 to 1.7, which are exemplified as values ​​that can normally be taken, for example, lower limit value: 0.1, upper limit value: 1.9, etc.). By determining that an abnormal condition exists and not adjusting the flow rate based on the correction value even when the correction value exceeds the upper or lower limit values, more stable control is possible and the accuracy of abnormality determination can be improved.

[0054] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0055] 1. Boiler 2 Boiler body 3 Blower (blowing means) 4 Flue 5 Fuel supply line (fuel supply passage) 6. Control device 61 Control section 62 Memory section 7 Damper 8 Combustion air pressure reducing member 9 Air flow rate detection unit (flow rate detection means) 11. On-off valve 12. On-off valve 13 Fuel supply adjustment valve 20 Burner 30 Air supply line

Claims

1. A supply means for supplying combustion air or fuel so that the flow rate corresponds to the amount of combustion; a flow rate detection means for detecting a flow rate of the combustion air or the fuel to be supplied; a correction value specifying means for specifying a correction value for making the air ratio fall within a predetermined range; a flow rate adjusting means for adjusting the flow rate of the fuel to be supplied or the flow rate of the combustion air to be supplied based on the correction value specified by the correction value specifying means and the flow rate of the combustion air detected by the flow rate detecting means or the flow rate of the fuel detected by the flow rate detecting means, the flow rate adjusting means does not adjust the flow rate based on the correction value when an abnormal condition exists because a change amount of the correction value exceeds a specific amount, The change in the correction value is the change between the correction value before control to change the combustion amount is started and the correction value after the flow rate of the combustion air or fuel supplied by the supply means becomes a flow rate corresponding to the changed combustion amount.

2. The boiler according to claim 1 , wherein the abnormal condition is established when an amount of change from an average value of the correction value specified by the correction value specifying means for a predetermined period of time exceeds the specified amount.

3. The boiler according to claim 2 , wherein an end point of the predetermined period is set to a timing that is a certain time before a current time.

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