JP2011012928A - Method of diagnosing combustion abnormality of heat treatment furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine not only an abnormality in a combustion system but also an abnormal portion and an abnormal form in a combustion facility.SOLUTION: In a combustion furnace having a plurality of combustion zones of a large number of burners 2 including air preheaters 4 for combustion air controlling a fuel system and a combustion air system by one system, such as a radiant tube furnace 1, temperatures of preheated air and exhaust gas of each of a large number of radiant tubes are detected. By comparing the detection values with a detection average value of the zone, presence/absence of an abnormality, an abnormal portion and an abnormal form of the combustion system are determined. Since the determination of presence/absence of the abnormality, the abnormal portion and the abnormal form of the combustion system in the furnace is permitted, deterioration is prevented, and necessary countermeasures are taken during operation. Maintenance plans are prepared beforehand. Thus, productivity, quality and energy efficiency in the combustion furnace are maintained by the minimum maintenance work at the minimum cost.

Description

  The present invention provides a heat treatment furnace having a plurality of combustion zones (hereinafter simply referred to as zones), each of which controls a fuel system and a combustion air system in a single system, of a plurality of burners attached with an air preheater for preheating combustion air. The present invention relates to a method for diagnosing combustion abnormality.

  For example, in a radiant tube furnace, in order to uniformly heat each of the plurality of zones 20 to an appropriate temperature, 50 to 300 small capacity burners 21 are installed in each zone 20 as shown in FIG. In FIG. 6, 22 is a combustion air pipe, 23 is a fuel pipe, 24 is a controller that controls the opening degree of the flow rate adjusting valves 25a and 25b provided in the combustion air pipe 22 and the fuel pipe 23, and 26 is an exhaust gas suction unit. Indicates a fan to play.

  A large number of burners installed in each of these zones generally control their fuel flow rate and combustion air flow rate in a single system mainly due to economic constraints.

  By the way, as shown in FIG. 7, the radiant tube is generally composed of three parts: the burner 21, a tube 27, and an air preheater 28 for recovering exhaust heat of the self-exhaust gas.

  The abnormal modes of the burner, tube, and air preheater constituting the radiant tube are as follows: clogging / melting damage for the burner, crack / perforation for the tube, etc. for the air preheater. Loss and leak.

  If the abnormality occurrence part of the three parts constituting the radiant tube can be identified at an early stage, the soundness of the radiant tube can be maintained by replacing the part in which the abnormality has occurred.

  However, if the abnormalities of the three components are left unidentified, the abnormal combustion continues, resulting in damage not only to the component in which the abnormality has occurred but also to the entire radiant tube.

  While a large number of radiant tubes arranged in each zone are controlling combustion air and fuel in a single system, if one of the radiant tubes is damaged, the combustion air to the other radiant tubes in the zone The balance of the fuel is lost, and a deviation occurs from normal combustion.

  As a result, not only does energy loss occur, but damage to other radiant tubes progresses in a chained fashion, causing major problems such as reduced production efficiency and poor product quality. Therefore, the maintenance cost is also enormous.

  Patent Document 1 discloses a method for determining whether or not burner combustion in such a heat treatment furnace is abnormal by detecting the temperature of each preheated air of a number of burners. The method disclosed in Patent Document 1 focuses on the fact that the preheated air temperature pattern changes due to a change in the air ratio.

  However, since the method disclosed in Patent Document 1 makes a determination based only on the temperature of the preheated air, it can only determine the abnormality of limited contents of the combustion system such as a burner, and the hole of the air preheater Judgment about abnormalities such as opening cannot be made. In addition, this method has a problem that the accuracy of specifying an abnormality is low because no consideration is given to the fact that the combustion air temperature varies depending on the fuel flow rate and the furnace temperature of the zone even at the same air-fuel ratio.

  Further, Patent Document 2 discloses a method for determining abnormal combustion of a burner by detecting the pre-pressure of a large number of burners. The method disclosed in Patent Document 2 determines whether or not combustion is abnormal by comparing a pre-measured pressure range during normal operation with a measured pre-pressure.

  However, since the method disclosed in Patent Document 2 also makes a determination based only on the pre-pressure of the burner, it can only determine abnormality of limited contents of the combustion system such as the burner, and the tube or air preheater. It is not possible to judge abnormalities such as hole opening.

   In addition, these Patent Documents 1 and 2 do not consider at all regarding the determination of an abnormal part or an abnormal form of a combustion facility.

JP-A-5-312318 Japanese Patent Laid-Open No. 8-13040

  The problem to be solved by the present invention is that the conventional method for diagnosing combustion abnormality in a heat treatment furnace can only determine the presence or absence of combustion abnormality of a limited content in a combustion system such as a burner.

The combustion abnormality diagnosis method for a combustion furnace according to the present invention includes:
In order to be able to determine not only abnormalities in combustion systems such as burners, but also abnormal parts and abnormal forms of combustion equipment such as tubes and holes in air preheaters,
In a combustion furnace provided with a plurality of combustion zones, each of which controls a fuel system and a combustion air system in a single system, of a large number of radiant tubes attached to an air preheater of combustion air,
Of the multiple radiant tubes,
1) Detect the temperature of each preheated air and exhaust gas,
Or
2) Detect the pre-burner pressure, preheated air and exhaust gas temperature,
By comparing these detection values with the detection average value of the zone, the main feature is to determine the presence / absence of abnormality in the combustion system and the abnormal part / abnormal form.

More specifically, when detecting the temperature of each preheated air and exhaust gas,
When both the preheated air temperature and the exhaust gas temperature are lower than the reference range with respect to the detected average value of the zone, it is determined that the burner or the pipe supplying fuel to the burner is clogged or blocked.

  Further, when both the preheated air temperature and the exhaust gas temperature are higher than the reference range with respect to the detected average value of the zone, it is determined that the tube has a hole or a crack.

  When the preheated air temperature is lower than the reference range and the exhaust gas temperature is higher than the reference range with respect to the detected average value of the zone, it is determined that the air preheater has melted or perforated.

On the other hand, when detecting the pre-burner pressure and the temperature of preheated air and exhaust gas,
If any of the pre-burner pressure, preheated air temperature, and exhaust gas temperature is lower than the reference range with respect to the detected average value of the zone, the fuel piping on the supply side is clogged or blocked from the pre-burner pressure measurement position. It is determined that

  Further, when the pre-burner pressure is higher than the reference range and the preheated air temperature and the exhaust gas temperature are lower than the detected average value of the zone, it is determined that the burner portion is clogged or blocked.

  Further, when the pre-burner pressure is higher than the reference range with respect to the detected average value of the zone and the preheated air temperature and the exhaust gas temperature are within the reference range, it is determined that the tube has been deformed.

  Further, when the preheated air temperature and the exhaust gas temperature are higher than the reference range and the pre-burner pressure is within the reference range with respect to the detected average value of the zone, it is determined that the tube has a hole or a crack.

  Also, if the preheated air temperature is lower than the reference range, the exhaust gas temperature is higher, and the pre-burner pressure is within the reference range, the air preheater will be melted or perforated. Is determined to have occurred.

  In the present invention, if the detection average value of the zone is obtained by extracting data in a range where the furnace temperature and the fuel flow rate are constant, the determination accuracy is further improved.

  According to the present invention, it is possible to determine the presence / absence of an abnormality in a combustion system in a combustion furnace, an abnormal part, and an abnormality form. Moreover, if warning values are set and trend management is performed, it is possible to grasp an abnormal part and an abnormal form before an obvious abnormality occurs.

  As a result of the above, it is possible to prevent deterioration or take necessary measures during operation and to plan maintenance in advance, and maintain productivity, quality, and energy efficiency in the combustion furnace with minimum maintenance work and cost. It becomes possible.

It is the figure which showed the apparatus which implements the 1st example of the combustion abnormality diagnosis method of this invention by detecting the preheating air temperature and waste gas temperature about a radiant tube furnace. (A) is the figure which showed the relationship of the zone furnace temperature of the zone 700 to 750 degreeC, and the preheating air temperature of one radiant tube with respect to the zone fuel flow rate of the range of 850 to 900 degreeC, (b) It is the figure which showed the relationship with exhaust gas temperature similarly. The exhaust gas temperature and the preheated air temperature of each radiant tube are extracted, and the average values thereof are shown. 1 zone, (b) is No. It is the figure which showed 2 zones. It is the figure which showed the apparatus which implements the 2nd example of the combustion abnormality diagnostic method of this invention by detecting a pre-burner pressure, preheating air temperature, and exhaust gas temperature about a radiant tube furnace. (A)-(c) is a figure explaining the example of a measurement of the 2nd example of the combustion abnormality diagnosis of this invention. It is the schematic of the combustion zone in a radiant tube furnace. It is a figure explaining the structure of a radiant tube.

  In the present invention, not only the abnormality of the combustion system, but also the purpose of making it possible to determine the abnormal part and form of the combustion facility, the temperature of each preheated air and exhaust gas, or each pre-burner pressure is also detected. These detection values were realized by comparing with the detection average value of the zone.

  If abnormalities occur in the combustion system of each burner of the multiple burners provided in the radiant tube furnace, it is natural that abnormalities are observed in each characteristic (pressure / temperature of each part, exhaust gas components, etc.). .

  However, it is not reasonable to always measure these characteristic values in view of economics and maintenance. Therefore, it is common to maintain after the event when the production efficiency and the fuel consumption rate are clearly deteriorated or when an abnormality is detected by periodic open inspection.

  On the other hand, if the number of measurement objects is limited to one (for example, combustion air temperature) as in the prior art, the burden on the economy and maintenance is reduced, and the “presence / absence” of abnormality is determined for a certain type of combustion abnormality. be able to. In this case, a certain effect can be obtained for measures during operation (combustion adjustment, burner closing, etc.) and during inspection (restriction of maintenance targets).

  However, in the case of the prior art, the contents of combustion abnormality that can be determined are limited, and it is impossible to determine in which part of the combustion system and in what form the abnormality has occurred. Therefore, it is impossible to finally determine the abnormal part and the abnormal form unless it is during open inspection, and the content corresponding to the abnormality is limited.

  The inventors conducted a comparative investigation of the abnormal part and abnormal form found during the open inspection of the combustion device in the radiant tube furnace and the measured values of various combustion characteristics. It was found that the form can be determined.

  In other words, the inventors can measure the preheated air temperature and exhaust gas temperature of each burner, or further each pre-burner pressure, and determine the abnormal part / abnormal form as well as the detection of the abnormal combustion burner. And it was found that it is possible to take measures at the time of inspection.

  The combustion abnormality diagnosis method for a combustion furnace according to the present invention has been made based on the knowledge of the inventors. Hereinafter, a case where the combustion abnormality diagnosis method according to the present invention is applied to a radiant tube furnace will be described.

[Example 1]
FIG. 1 shows a configuration example when a first example of the combustion abnormality diagnosis method of the present invention is applied to a radiant tube furnace by detecting a preheating air temperature and an exhaust gas temperature.
Reference numeral 1 denotes a zone of a radiant tube furnace, and a plurality of burners 2 are provided in each zone 1 in order to perform zone heating. Each burner 2 in the zone 1 is supplied with fuel and combustion air in one system, and the respective flow rates are zone-controlled.

  After the combustion air exchanges heat with the exhaust gas in the air preheater 4, the combustion air is led to the burner 2, mixed with the fuel and burned in the tube 3 to indirectly heat the object. 1, 5 is a fuel pipe, 6 is a combustion air pipe, 7 is an exhaust gas pipe, 14a and 14b are flow control valves provided in the fuel pipe 5 and the combustion air pipe 6, and 15 is provided in the exhaust gas pipe 7. The exhaust gas suction fan is shown.

  When carrying out the method of the present invention, the preheated air temperature measuring device 9 is provided in the combustion air piping 6 on the downstream side of the air preheater 4 and the exhaust gas temperature measuring device 10 is provided in the exhaust gas piping 7 of each burner 2 in the radiant tube furnace configured as described above. Is installed.

  Then, each measurement data measured by the preheating air temperature measuring device 9 and the exhaust gas temperature measuring device 10 is sent to the data processing device 13 via the data collecting device 11 and the data storage unit 12. Based on the two types of data measurement values, the data processing device 13 determines the presence / absence of abnormality in the combustion system and the abnormal part / abnormal form as follows. The data storage unit 12 and the data processing device 13 may not be divided, and an integrally configured device may be used.

  In Table 1 below, the abnormal part and abnormal form found during the open inspection of the combustion device in the radiant tube furnace and the measured values of various combustion characteristics were found and compared with the abnormal part and abnormal form. The relationship between the measured value of data and the difference between the detected average value of the zone is shown.

  As shown in Table 1, if the preheated air temperature and exhaust gas temperature are measured for each radiant tube and these detected values are compared with the detected average value of the zone, not only the presence or absence of abnormality in the combustion system, It can be seen that the form can also be determined.

  That is, when the preheated air temperature is low and the exhaust gas temperature is low, it is determined that the burner or the pipe that supplies fuel to the burner is clogged or blocked. This is because when the burner or the fuel pipe is clogged or blocked, the fuel is not sufficiently supplied, the exhaust gas temperature is lowered, and as a result, the preheated air temperature is also lowered.

  Further, when the preheating air temperature is low and the exhaust gas temperature is high, it is determined that the air preheater is melted. This is because when the heat recovery of the self-exhaust gas is not sufficiently performed due to melting of the air preheater or the like, the preheating air temperature decreases and the exhaust gas temperature increases.

  Further, when the preheated air temperature is high and the exhaust gas temperature is high, it is determined that a hole or a crack has occurred in the tube. This is because when the tube has holes or cracks, the high-temperature atmosphere gas in the furnace is drawn into the tube from the holes or cracks in the tube, and the exhaust gas temperature rises due to the heat energy. This is because the preheating air temperature also rises.

  Therefore, an abnormal pattern corresponding to the difference between each measured value and the detected average value of the zone is set in advance in the data processing device, and the preheated air temperature and exhaust gas temperature measured for each radiant tube are detected average of the zone. By comparing with the value, it is possible to determine not only the presence / absence of abnormality but also the abnormal part / abnormal form.

  At this time, the normal ranges of the preheated air temperature and the exhaust gas temperature vary depending on the type of the furnace and the radiant tube, and therefore it is desirable to set them after conducting a preliminary survey. However, compared with the majority of normal burners, the burner in which an abnormality has occurred has a temperature deviation. Set it.

  Further, it is desirable to set a value and an abnormal pattern for displaying an abnormality or warning in advance in the data processing apparatus, and to display the abnormal pattern together with an alarm when an abnormality occurs.

  In addition, the value which should display abnormality or a warning is not decided uniformly, but is suitably determined by the type of a radiant tube furnace and the apparatus which comprises it, or the view of maintenance.

  Furthermore, if trend management of each measurement value is performed, it is possible to take means for preventing the progress of abnormality.

  FIG. 2 shows the relationship between the preheated air temperature of one radiant tube and the exhaust gas temperature with respect to the zone fuel (C gas) flow rate in the range where the zone furnace temperature is 700 ° C. to 750 ° C. and in the range of 850 ° C. to 900 ° C.

  From FIG. 2, it is clear that the preheated air temperature and exhaust gas temperature are affected not only by the fuel flow rate of the zone but also by the furnace temperature of the zone. descend.

  Therefore, in order to improve the analysis accuracy, the preheated air temperature and the exhaust gas temperature are sampled and accumulated in a certain period and a certain period, and then the data of the zone in which the zone furnace temperature and the fuel flow rate are in a certain range are extracted, It is desirable to take an average value.

  In the sampling hole of the combustion air piping and exhaust gas piping of the radiant tube furnace of the hot dip galvanized steel sheet production line, a sheath thermocouple is installed as the preheating air temperature measuring device and exhaust gas temperature measuring device, and in each of the following data extraction ranges, The exhaust gas temperature and preheated air temperature of the radiant tube were detected.

(Data extraction range)
Furnace temperature: 850 ° C or higher and 900 ° C or lower Fuel:
Type: C gas (4600kcal / Nm ³ )
Flow rate: 180Nm ³ / H or more, 200Nm ³ / H below

  The data storage unit 12 samples the furnace temperature and zone fuel flow rate of the zone at that time for 3 days at an interval of 1 minute, and the data processing unit 13 exhausts the exhaust gas temperature and preheating of each radiant tube in the constant furnace temperature range and fuel flow rate range. The air temperature was extracted and the average value was taken.

  FIG. 3 shows the output of the data processing device 13. FIG. 1 zone output, (b) No. The output of 2 zones is shown.

  No. shown in FIG. In one zone, the preheated air temperature and exhaust gas temperature of the No. 3 radiant tube were both low, and burner abnormality was determined. Moreover, since the preheating air temperature of the No. 9 radiant tube was low and the exhaust gas temperature was high, it was determined that the air preheater was abnormal.

  No. shown in FIG. In zone 2, the preheated air temperature and exhaust gas temperature of the No. 5 radiant tube were both high, and the tube was judged abnormal.

  And the said determination became clear as a result of the radiant tube inspection of a subsequent periodic repair.

[Example 2]
FIG. 4 shows a configuration example in the case where the second example of the combustion abnormality diagnosis method of the present invention is applied to a radiant tube furnace. 4, the same reference numerals as those in FIG. 1 denote the same parts or corresponding parts, and detailed description thereof is omitted.

  When the second example of the method of the present invention is implemented, in addition to the configuration of the first example shown in FIG. 1, a pre-burner pressure measuring device 8 is further installed in the fuel pipe 5 of each burner 2.

  Each measurement data measured by the pre-burner pressure measuring device 8, the preheating air temperature measuring device 9, and the exhaust gas temperature measuring device 10 is sent to the data processing device 13 via the data collecting device 11 and the data storage unit 12.

  Based on the three types of data measurement values, the data processing device 13 determines whether there is an abnormality in the combustion system and the abnormal part / abnormal form as follows.

  In Table 2 below, the abnormal part and abnormal form found during the open inspection of the combustion device in the radiant tube furnace and the measurement values of various combustion characteristics were found, and the abnormal part and abnormal form were found. The relationship between the measured value of data and the difference between the detected average value of the zone is shown.

  As shown in Table 2, if the pre-burner pressure, preheated air temperature, and exhaust gas temperature are measured for each burner and these detected values are compared with the detected average value of the zone, It turns out that it becomes possible to determine a site | part and an abnormal form.

  Therefore, an abnormal pattern corresponding to the difference between each measured value and the detected average value of the zone is preset in the data processing device, and the pre-burner pressure, preheated air temperature, and exhaust gas temperature measured for each burner are set in the zone. Compared with the detected average value, it is possible to determine not only the presence / absence of abnormality but also the abnormal part / abnormal form.

FIG. 5 shows an example of measurement results according to the present invention.
According to this measurement result, no. The burner No. 2 has a lower preheated air temperature and a higher exhaust gas temperature, which exceeds the abnormality determination value, which is consistent with the abnormality pattern E in Table 2. For the burner No. 2, it can be determined that the air preheater is melted or perforated. Therefore, fire extinguishing measures were taken, and a spare air preheater was prepared and replaced by the next maintenance date.

  No. The burner No. 5 has a higher pre-burner pressure, a lower preheated air temperature and a lower exhaust gas temperature, each exceeding a warning value, and is consistent with the abnormal pattern B in Table 2. Regarding the burner No. 5, it can be determined that clogging or blockage has occurred at the burner portion. Therefore, the operation was performed after the air ratio was optimally adjusted by the valve of the combustion air piping, and the burner was cleaned on the next maintenance day.

  On the other hand, in the case of the prior art, as described above, the abnormality of the combustion system cannot be so-called “diagnosed”, and only the abnormality is detected. For example, in the detection method using the preheated air temperature as an index disclosed in Patent Document 1, an abnormality due to the abnormal patterns A, B, D, and E in Table 1 can be detected, but an abnormal pattern of C cannot be detected. It cannot be determined in what form it occurs.

  The present invention is not limited to the above example, and it goes without saying that the embodiments may be changed as appropriate within the scope of the technical idea described in each claim.

  For example, although the U-shaped radiant tube is used in the embodiment of FIG. 1 and the W-shaped radiant tube is used in the embodiment of FIG. 4, the present invention can be applied even when a single-ended radiant tube is used. Further, if the influence of variation is not taken into consideration, the data may not be accumulated and the evaluation may be performed using instantaneous values at the same furnace temperature and the same fuel flow rate. Furthermore, not only a hot dip galvanizing line but any combustion furnace that uses a radiant tube is applicable.

  If the present invention described above is a heat treatment furnace having a plurality of combustion zones in which a fuel system and a combustion air system are controlled in a single system, a combustion abnormality of a radiant tube furnace, if there are a plurality of burners attached with an air preheater for combustion air. It is effective not only for diagnosis but also for combustion abnormality diagnosis of other combustion furnaces.

DESCRIPTION OF SYMBOLS 1 Zone 2 Burner 3 Tube 4 Air preheater 5 Fuel piping 6 Combustion air piping 7 Exhaust gas piping 8 Burner pre-pressure measuring device 9 Preheating air temperature measuring device 10 Exhaust gas temperature measuring device 11 Data collection device 12 Data storage part 13 Data processing device

Claims (13)

In a combustion furnace provided with a plurality of combustion zones each controlling a fuel system and a combustion air system in a single system of a plurality of radiant tubes attached with an air preheater of combustion air,
Detecting the temperature of each preheated air and exhaust gas of the multiple radiant tubes;
A method for diagnosing combustion abnormality in a combustion furnace, wherein the presence or absence of abnormality of the combustion system and the abnormal part / abnormal form are determined by comparing these detected values with the detected average value of the zone. For the detection average value of the zone,
If both the preheated air temperature and exhaust gas temperature are lower than the reference range,
2. The combustion abnormality diagnosis method for a combustion furnace according to claim 1, wherein it is determined that the burner or a pipe for supplying fuel to the burner is clogged or blocked. For the detection average value of the zone,
If both the preheated air temperature and exhaust gas temperature are higher than the reference range,
The combustion abnormality diagnosis method for a combustion furnace according to claim 1, wherein it is determined that a hole or a crack has occurred in the tube. For the detection average value of the zone,
If the preheating air temperature is lower than the reference range and the exhaust gas temperature is higher than the reference range,
2. The combustion abnormality diagnosis method for a combustion furnace according to claim 1, wherein the air preheater is determined to have melted or perforated. For the detection average value of the zone,
When both the preheating air temperature and the exhaust gas temperature are lower than the reference range, it is determined that the burner or the piping that supplies fuel to the burner is clogged or clogged.
If both the preheated air temperature and the exhaust gas temperature are higher than the reference range, it is determined that a hole or crack has occurred in the tube.
The combustion abnormality in a combustion furnace according to claim 1, wherein when the preheating air temperature is lower than the reference range and the exhaust gas temperature is higher than the reference range, it is determined that the air preheater has melted or perforated. Diagnosis method. In the combustion abnormality diagnostic method according to claim 1,
Further detecting the pre-burner pressure of each of the multiple radiant tubes;
A method for diagnosing combustion abnormality in a combustion furnace, wherein the presence or absence of abnormality of the combustion system and the abnormal part / abnormal form are determined by comparing these detected values with the detected average value of the zone. For the detection average value of the zone,
If any of the pre-burner pressure, preheating air temperature, and exhaust gas temperature is lower than the reference range,
The combustion abnormality diagnosis method for a combustion furnace according to claim 6, wherein it is determined that clogging or blockage has occurred in the fuel pipe on the supply side from the pre-burner pressure measurement position. For the detection average value of the zone,
If the pre-burner pressure is high and the preheating air temperature and exhaust gas temperature are low above the reference range,
7. The combustion abnormality diagnosis method for a combustion furnace according to claim 6, wherein it is determined that the burner portion is clogged or blocked. For the detection average value of the zone,
If the pre-burner pressure is higher than the reference range and the preheated air temperature and exhaust gas temperature are within the reference range,
The combustion abnormality diagnosis method for a combustion furnace according to claim 6, wherein it is determined that deformation has occurred in the tube. For the detection average value of the zone,
If the preheated air temperature and exhaust gas temperature are higher than the reference range and the pre-burner pressure is within the reference range,
7. The combustion abnormality diagnosis method for a combustion furnace according to claim 6, wherein it is determined that a hole or a crack has occurred in the tube. For the detection average value of the zone,
If the preheated air temperature is lower than the reference range, the exhaust gas temperature is high, and the pre-burner pressure is within the reference range,
The combustion abnormality diagnosis method for a combustion furnace according to claim 6, wherein it is determined that the air preheater has melted or perforated. For the detection average value of the zone,
If all of the pre-burner pressure, preheated air temperature, and exhaust gas temperature are lower than the reference range, it is determined that the fuel pipe on the supply side is clogged or blocked from the pre-burner pressure measurement position.
If the pre-burner pressure is higher than the reference range, and the preheating air temperature and exhaust gas temperature are low, it is determined that the burner section is clogged or clogged,
If the pre-burner pressure is higher than the reference range and the preheated air temperature and exhaust gas temperature are within the reference range, it is determined that the tube has been deformed,
If the preheated air temperature and exhaust gas temperature are higher than the reference range and the pre-burner pressure is within the reference range, it is determined that the tube has perforated or cracked,
When the preheating air temperature is lower than the reference range, the exhaust gas temperature is high, and the pre-burner pressure is within the reference range, it is determined that the air preheater has melted or perforated. 6. The combustion abnormality diagnosis method according to 6.   The combustion abnormality diagnosis method according to any one of claims 1 to 12, wherein the detected average value of the zone is obtained by extracting data in a range in which the furnace temperature and the fuel flow rate are in a certain range.

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