JP2808454B2 - Fire detector for rotary air preheater - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detection device for an air preheater installed in an exhaust gas system of a boiler in a thermal power plant, for example.

2. Description of the Related Art FIG. 12 shows a schematic configuration of a Jungstrom-type air preheater often used as an air preheater installed in a thermal power plant as an example of a conventional technology.

In FIG. 12, the rotor main body has a heating element 3 filled between a plurality of partition plates 2 radially mounted in the rotor outer cylinder 1 as a main component, and is provided on the outer peripheral surface of the rotor outer cylinder 1. The pinion 5 (or gear) meshing with the provided pin rack 6 (or gear) is driven by the drive motor 4 so that the rotor body slowly rotates in the direction of arrow C about the central rotation shaft (not shown). It has become.

Ducts installed at both upper and lower ends of the rotor body are divided into two sections, respectively, and are filled between an exhaust gas inlet duct 7 that guides high-temperature exhaust gas that has passed through the flue in the direction of arrow A and a large number of partition plates 2. Exhaust gas, which has been deprived of heat by contact with the heating element 3, forms an exhaust gas duct by an exhaust gas outlet duct 8 which passes in the direction of arrow A ′ and goes to the chimney, while a preheated air inlet duct 9 has a The cold air flowing to the rotor main body is brought into contact with the high-temperature heating element 3 to heat the cold air, pass through the preheated air outlet duct 10 in the direction of arrow B 'and send it to the boiler combustion furnace.

Heating element 3 in rotating rotor body
Is the main component of an air preheater that performs efficient heat exchange by storing heat during a half rotation that contacts hot gas and heating during a half rotation that contacts cold air.

Thus, in the Jungstrom type air preheater described above, exhaust gas entering the rotor body is usually 40%.
At about 0 ° C., a small amount of unburned components such as ash may be mixed, and these unburned components are formed on the uneven surface to increase the heat exchange efficiency. May accumulate on and accumulate on fire, igniting and developing into a fire accident.

In order to prevent such a large accident as described above, it is necessary to detect and treat the heating element portion of the rotor body having an abnormal temperature at an early stage, and an infrared sensor as shown in FIG. The heating element 3 can be monitored from the axial end surface (in this example, the upper end surface) of the rotor body to the partition plate 2 by using the reference numeral 21.

That is, the infrared sensor 21 is swingably attached to the rotation center portion 24 provided on the outer stationary portion of the rotor outer cylinder 1 via the arm 25, and this is indicated by a dashed line with a radius R from the rotation center portion 24. 26 by rotating on the
The inside of the rotating rotor body is monitored evenly. Then, an infrared ray indicated by an arrow D radiated from one of the heating elements 3 is condensed by a lens 22 provided on the infrared sensor 21 so as to impinge on a sensor element 23 provided inside the sensor. ing.

FIG. 14 shows an example of a specific conventional technique for moving such an infrared sensor 21 that can swing freely.

In FIG. 14, infrared rays D generated from the heating element 3 in the rotor body of the Jungstrom type air preheater travels in the direction of the arrow, and is condensed.
The sensor element 23 inside the infrared sensor 21 (the thirteenth
(Refer to the figure.)
From the outside.

The infrared sensor 21 is connected to a gear head 62 by an arm 25, and is connected to an arm by an external reciprocating drive device (not shown).
Driven through the gear 25, the head swings about the gear head 62 to scan the upper end surface of the rotor main body.

To make the sensor element withstand the high temperature atmosphere in the duct 8, the sensor element in the infrared sensor 21 is provided with a cooling water pipe.
Cooled by water flowing through 64.

In addition, since the surface of the lens 22 of the infrared sensor 21 is contaminated with ash or the like in the exhaust gas, the dirt can be periodically removed by an air jet ejected from the air nozzle 65 and cleaned. .

Further, the output of the infrared sensor 21 is compared with a preset reference value, and if it exceeds the reference value, an abnormal alarm is generated.

In addition, 66 is a lens cleaning air pipe, and 67 is a link handle connected to an external reciprocating drive device.

As another conventional technique, there is also known a method of monitoring the temperature of the heating element 3 by linearly reciprocating in the radial direction on the end face of the rotor body instead of swinging the infrared sensor 21. .

FIG. 15 shows a conventional example of such a device, in which a housing 11 is provided on the lower end surface side of an outer stationary portion of a rotor outer cylinder 1 (see FIG. 12), and a rotor body of the housing 11 is provided therefrom. The rail 12 is provided to the rotation center side, and the infrared sensor 21 is moved forward and backward by the driving device 13 via the rod 14.

Reference numeral 15 denotes a wheel provided on the rail 12 and provided on the infrared sensor 21.

The infrared sensor 21 is provided with a condensing lens 22. The sensor 21 that has received infrared light indicated by an arrow D from above through the lens 22 outputs a signal to the signal amplifier 16.

If the lens 22 of the infrared sensor 21 becomes dirty, the transmission of infrared light deteriorates, and the infrared light does not show the correct infrared intensity.Therefore, the infrared sensor 21 is periodically drawn into the housing 11 and air is blown from the air nozzle 17. , Lens 22
Try to clean the surface.

At this timing, the electromagnetic valve controller 19 recognizes that the infrared sensor 21 has entered the housing 11 by, for example, pressing the microswitch 20, and the air nozzle 17
By opening the electromagnetic valve 18 connected to the scanning, the scanning is performed at the end of each scanning or at an appropriate time period.

Some infrared sensors do not have a convex lens as shown in FIG. This infrared sensor 21 '
The infrared ray D transmitted through the cover glass 27 attached to the front surface side is condensed by the concave mirror 28 as shown by an arrow, and is applied to the internal sensor element 23. Therefore, in such an infrared sensor 21 ', the object to be cleaned is the cover glass 27 on the front side where the infrared light D is incident.

Problems to be Solved by the Invention The conventional fire detection devices described above, however, have the following problems.

(1) The infrared sensor 21 itself moves in a high-temperature atmosphere, and the sensor element 23
Has a low heat-resistant temperature, and may be damaged by heat or output may be unstable. Therefore, as shown in FIG. 14, it is necessary to cool the sensor element, and therefore, equipment for a cooling device such as the pipe 64 is required.

(2) The infrared sensor 21 is a lens 22 for the purpose of increasing sensitivity.
Is used to focus the light on the sensor element 23. However, since the infrared rays from the non-monitoring section come out from between the narrow partition plates 2, the sensor
The 21 can only monitor the area directly below it.

(3) The lens of the infrared sensor 21 (the sensor 21 'in FIG. 16)
Then, since the surface dirt on the cover glass 27) receives infrared rays, that is, variously changes depending on the atmosphere in the place where the temperature is to be monitored, dirt that cannot be removed by merely periodically cleaning with an air jet occurs. .

In particular, when the infrared sensor 21 is installed on the lower end surface side of the rotor main body, ash and unburned components dropped from the heating element 3 adhere to the lens 22 surface. The countermeasures do not remove enough dirt.

(4) In the steady state, when the infrared intensity output decreases,
It is not clear whether the sensor surface cleaning is defective or the sensor is abnormal.

(5) The output from the sensor element 23 is a continuous output that is output according to time and position, and there is no position information of the abnormal temperature point only by the absolute value or relative change of this value.
Therefore, the reliability of abnormality detection is poor.

(6) In the swing type infrared sensor 21 shown in FIGS. 13 and 14, since the signal output line 61 and the cooling water pipe 64 swing around according to the swing of the sensor 21, there is a problem in durability.
If a part of the infrared sensor 21 breaks down, it cannot be removed and repaired unless it enters the duct 8.

Means for Solving the Problems In order to solve the problems of the prior art described above, the present invention relates to a rotary air preheater having a rotating rotor, which is disposed on a preheated air inlet dust side of a rotor main body, and is provided between partition plates. A mirror that linearly reciprocates in the vicinity of the heating element filled with the mirror and reflects infrared rays emitted from the heating element, and a sensor that detects the infrared rays emitted by the heating element and reflected by the mirror A device that performs image processing on the detection output of this sensor as information and displays the temperature information of the heating element in accordance with the position of the mirror; and a housing in which the sensor or the sensor and the mirror are housed. Means for emitting infrared light of a constant intensity, provided so as to face the sensor or the mirror, and emitting from the means. Means for comparing a detected value obtained by detecting the emitted infrared light with the sensor with a reference value, and means for cleaning the surface of the sensor or the mirror when the detected value is lower than the reference value,
Means for comparing again a detection value of infrared light emitted from the emission means and a reference value after emitting the infrared light from the emission means and determining whether or not the sensor is abnormal. To provide a fire detection device.

According to the present invention, only the mirror relatively resistant to high temperature and contamination reciprocates linearly on the object and reflects infrared rays to the infrared sensor side, so that the sensor receives radiant heat from the heating element. There is no.

According to the invention, in addition, the detected instantaneous change in the infrared intensity is displayed continuously as a change in brightness or color at the corresponding position on the display, depending on the relative position of the heating element and the mirror. Is done.

According to the present invention, in addition, a difference between two or more different images over time is calculated for an image displayed on the display, and the difference is compared with a preset reference value. Alarm.

According to the present invention, dirt on the surface of the sensor or the mirror can be reliably removed by monitoring while comparing it with the reference infrared intensity, and at the same time, the sensor sensitivity can be monitored to detect a sensor abnormality. .

Embodiments Embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 5 show an embodiment in which the present invention is applied to a Jungstrom-type air preheater as exemplified in FIG.

In FIG. 1, a mirror 31 in the form of a plane mirror is provided above the upper end face of the rotor body in the air preheater, thereby reflecting infrared rays D emitted from the heating element 3 filled between the partition plates, The light is condensed by a lens 22 of an infrared sensor outside the rotor outer cylinder 1 and is detected by an infrared sensor element 23. The information obtained by the infrared sensor element 23 is sent to the image processing device 33, and a temperature distribution is drawn on the display 34 in a plan view of the rotor main body.

FIG. 2 shows an example in which the above-described mirror 31 is provided at the tip of a drive rod 71 which can linearly reciprocate in the radial direction of the rotor body.

Therefore, the mirror 31 linearly reciprocates in the radial direction on the upper end surface of the rotor body via the driving rod 71,
The infrared rays emitted from the heating element 3 are reflected and sent to an infrared sensor.

Reference numeral 72 is a guide for guiding the movement of the drive rod 71.

FIG. 3 shows an example of a mounting structure of the mirror 31 and the driving rod 71.

In FIG. 3, a driving rod 71 is formed of a hollow rod, and a mirror 31 is attached to a tip of the driving rod 71 at a required inclination angle via a pin 73, and reflects an infrared ray D from a heating element immediately below as shown by an arrow. Through the drive rod 71 to the infrared sensor.

The attachment of the mirror 31 may be fixed, but is preferably a mirror.
Can be installed so that 31 tilt angles can be adjusted.

Further, when air for cleaning the reflection surface of the mirror 31 is required, the hose can be passed through the drive rod 71, so that the hose can be prevented from being exposed to hot air.

FIG. 4 shows another example of a device for reciprocating the mirror 31 linearly.

In FIG. 4, the mirror 31 is attached to the lower end of the holder 74 at a required inclination angle. The holder 74 is connected to the drive wire 43 at a portion indicated by reference numeral 75 on the upper end side.
The drive wire 43 is fixed and is driven by the drive motor 13 via the plurality of pulleys 44, so that the holder 74 on which the mirror 31 is mounted can reciprocate on the rail 12 via the wheels 15. I have.

FIG. 5 shows the mirror 31 in the form of a plane mirror shown in FIG. 4 instead of the mirror 31 'in the form of a concave mirror. The other construction is the same as that in FIG. Description is omitted.

Thus, replacing the mirror 31 in the form of a plane mirror shown in FIG. 4 (and FIGS. 1 to 3) with the mirror 31 'in the form of a concave mirror has the following advantages.

That is, the infrared rays emitted from the heating element just below the mirror are not perfectly parallel rays, and the light rays D which spread with a slight divergence as shown in FIG.
Therefore, by reflecting 90 ° with this concave mirror 31 ',
Light can be efficiently collected on the infrared sensor.

Next, the present invention will be described with reference to FIGS.

The present invention relates to a specific means for displaying the infrared intensity detected by the infrared sensor 21 on the display 34 shown in FIG.

That is, the infrared rays radiated from the heating element 3 of the rotor main body are condensed by the infrared sensor 21 and output from an amplifier (not shown) as an electric signal proportional to the infrared intensity, and the display 34 corresponding to the position of the mirror 31 is displayed.
Displayed on the screen above. The method of displaying on the display 34 in color or luminance in proportion to the electric signal is a general technique, and the description is omitted.

Then, the rotor body rotates at a certain speed,
31 reciprocates linearly at a constant speed, and if the infrared intensity is displayed on the screen of the display 34 in a fixed order according to time, an image such as that shown in FIG. 6 can be obtained.

Here, on the screen of the display 34, a basic pattern of the rotating rotor body is drawn in advance, and by switching the position number over time, an infrared intensity pattern of the entire surface is drawn on the screen. .

FIG. 6 shows a display 34 in which the circumference of the upper surface of the rotatable rotor body is divided into, for example, 16 portions, and each boundary is numbered from 1 to 16 and displayed. The infrared intensity is displayed in color or luminance at a time point corresponding to the moving position of the infrared sensor 21.

For example, there is an infrared intensity gradient from the periphery to the center, and if it is expressed by dividing it at an appropriate level,
As shown by reference numerals 51, 52, and 53, a stair-like pattern is appropriately formed on the display. However, if there is an abnormal temperature portion in part, the above-described pattern is distorted, and a discontinuous point indicated by reference numeral 54 occurs. This discontinuous pattern is displayed as a time change by rewriting the display on the display 34 when the infrared sensor 21 moves and comes to the same position again.

7A, 7B, and 7C show examples of images that have changed over time.

Now, the infrared intensity distribution produced at time T ₀ is
7A), for example, even if a high luminance is given to a strong infrared intensity and a high luminance as indicated by reference numeral 54 exists on the screen, the bright spot can be detected by the infrared intensity detection system only on this screen. May be a malfunction.

However, this bright spot 54 is displayed on screen 2 at time T ₁ (FIG. 7B),
As the screen 3 at time T ₂ (the Figure 7C), around the same position, expanded areas of progressively higher intensity point, and if observed that continuously its center position changes, clearly abnormal It can be recognized that the state is expanding.

If the output from the infrared sensor merely changes continuously with respect to time, for example, the sensor scan at the same position may exceed a certain luminance level several times in a row or have high luminance. By giving a condition that the output duration is long, an effect similar to that seen in a pattern can be expected, but there is a great difference in the reliability compared to a pattern that appeals to the eye.

Next, a means for observing such an abnormal state more clearly will be described with reference to FIG.

Screen 1 is an image obtained in time T ₀ (see FIG. 7A), the screen 3 is [Delta] T time has elapsed from the time _{T 0 (ΔT = T 2 -T} 0) after the image at time T ₂ (cf. Figure 7C ). When the screen 1 is subtracted from the screen 3, a difference 55 occurs if the abnormal portion in the screen is enlarged. When the difference is calculated, for example, by calculating the area or by multiplying the area by the luminance (infrared ray intensity) with a predetermined reference value, and when the value of the predetermined number of times exceeds the reference value If an alarm is issued, a false alarm due to a disturbance is prevented, and the observer does not need to continuously observe.

The method of creating this difference screen is as follows: screen 2-screen 1, screen 3-
Screen 1, Screen 3-Screen 2, or Screen N-Screen (N-
It is needless to say that appropriate cases can be adopted, for example, in the case of relative evaluation in which 1) etc. and the reference screen are set to the immediately preceding screen, or in the case where a certain reference screen such as screen 1 is compared with the absolute difference by taking a difference. . Then, these arithmetic processes are performed by the image processing device 33, and the results are displayed on the display.

Next, the present invention will be described with reference to FIGS.

9 to 10 show a first embodiment of the present invention, in which a mirror 31 can linearly reciprocate in the radial direction of the rotor main body on the end face of the rotor main body in the Jungstrom type air preheater illustrated in FIG. Is configured.

The reciprocation of the mirror 31 is performed by the device shown in FIG. That is, the drive wire 43 is
Is driven through the plurality of pulleys 44, whereby the holder 74 reciprocates on the rail 12 via the wheels 15, thereby moving the mirror 31 attached to the holder 74 at a required inclination angle. It has become.

Then, the infrared sensor is set so that the reflected light of the infrared ray D reflected by 90 ° by the reciprocating mirror 31 is incident.
21 is provided in the housing 11. Infrared sensor 21
Is equipped with an electronic cooling element, which is controlled to cool or heat so as to maintain a substantially constant temperature without being affected by the environmental temperature. Reference numeral 35 denotes a heat sink of the electronic cooling element.

Further, on the upper surface in the housing 11, a radiation plate 36 whose surface is colored black, for example, by anodizing, and a heater 37 closely attached to the back surface of the radiation plate 36 are provided. Then, a thermocouple 38 is directly attached to the radiation plate 36, and based on the output of the thermocouple 38, the supply current to the heater 37 is controlled so that the surface temperature of the radiation plate 36 becomes constant. A power supply controller 39 is provided.

Further, a water / detergent nozzle 40 is provided so as to pass through the center of the electric nozzle 17. A cleaning detergent and water are supplied to the water / detergent nozzle 40 via a water / detergent switching electromagnetic valve 41 and a water supply electromagnetic valve. These solenoid valves 41 and 42 are the air solenoid valve 18 and the microswitch 2.
0 and further connected to and controlled by an electromagnetic valve controller 19 connected to a signal amplifier 16 for amplifying a signal from the infrared sensor 21.

Reference numeral 45 denotes an air nozzle that constantly blows air near the surface of the lens 22 of the infrared sensor 21. This forms an air curtain to protect the lens 22 from dirt. Similarly, 46 is an air nozzle, and the housing 11
An air curtain near the entrance of the building.

Now, in the device configured as described above, when the mirror 31 enters the housing 11 after finishing a certain traverse, a part of the support is
Is pressed, whereby the power supply controller 39 and the solenoid valve controller 19 are started.

First, the power supply controller 39 starts energization of the heater 37, controls the current of the heater 37 with reference to the thermocouple 38, and keeps the surface temperature of the radiation plate 36 constant. Therefore, the mirror 31 reflects the infrared light D of a constant intensity radiated from the radiation plate 36, and
The light is condensed on the sensor element in the sensor through the lens 22.

Since the infrared radiation emitted from the radiation plate 36 is constant, the mirror
If the surface of 31 or lens 22 is not dirty, infrared sensor
21 should show a constant output.

Therefore, taking advantage of this fact, a change in the sensitivity of the mirror 31 and the infrared sensor 21 and a countermeasure for cleaning the surface are performed in the following procedure.

(1) The signal amplifier 16 compares the output of the infrared sensor 21 with a preset reference value. When the sensor output is lower than the reference value, the controller 19 first opens the solenoid valve 18 and sets the air nozzle for a certain time. An air jet is sprayed on the mirror 31 from 17.

(2) When the output of the infrared sensor 21 does not recover, the electromagnetic switching valve 41 is switched to the water side, the electromagnetic valve 42 is opened for a certain period of time, and the water jet from the water / detergent nozzle 40 is mirrored.
Spray to 31.

(3) If the output of the infrared sensor 21 still does not recover, the electromagnetic switching valve 41 is switched to spray the detergent from the water / detergent nozzle 40 to the mirror 31 so that the water is continuously sprayed.

(4) Infrared sensor by the above procedures (1) to (3)
When the output of 21 does not recover, it is determined that the sensor element is abnormal, and the controller 19 issues an alarm.

In this case, the lens 22 is protected from dirt by an air curtain made by the air nozzle 45.However, the position of the infrared sensor 21 is set in FIG. May be moved to the right back of the camera.

FIG. 11 shows another embodiment, and the difference from the embodiment shown in FIG.
The device itself is reciprocated on a rail 12 via a rod 14 and wheels 15 by a driving device 13 as in the conventional example shown in FIG.

Therefore, in this case, the object to be cleaned is the focusing lens 22 of the infrared sensor 21 and this lens
22 is cleaned by a method similar to that shown in FIG.

Note that, in the embodiment shown in FIG.
It can also be moved by a driving rod 14 as shown in FIG.

Further, in the embodiment shown in FIGS. 10 and 11, for example, as shown in FIG. 10, by including the image processing device 33 and the display 34 as shown in FIGS. Provided is a temperature monitoring device which is capable of giving a reliable and accurate situation judgment to a monitor in addition to performing the surface cleaning of an infrared sensor accurately.

Further, the means for cleaning dirt of air / water / detergent in the embodiment shown in FIG. 11 is applicable even if the infrared sensor 21 is of a swing type as shown in FIGS. 13 and 14. Things.

Effects of the Invention As described above, according to the present invention, only a mirror relatively resistant to high temperature and contamination moves on an object, reflects infrared rays to the infrared sensor side, and the sensor reduces radiant heat from the object. Since the sensor element is not affected, it is not necessary to cool the sensor element which is vulnerable to high temperature in the sensor, so that a special cooling device is not required. In this case, since the mirror reciprocates linearly, the drive mechanism is simplified as compared with the swinging infrared sensor, and the mechanical reliability of the system is improved.

Further, by performing image processing on information from the infrared sensor, it is easy to grasp the position of the object at an abnormally high temperature and to recognize a temporal change, and the initial fire extinguishing is performed promptly.

Then, according to the invention, furthermore, by the relative position of the object and the mirror, to the corresponding position on the display,
Since the detected infrared intensity change is displayed continuously as a change in brightness or color, the temporal and positional change can be more reliably observed.

Furthermore, according to the present invention, since a difference between two or more different images over time is calculated for an image displayed on the display, a difference between the difference and a preset reference value is calculated. An alarm can be issued by comparison, so that a false alarm due to disturbance is prevented, and the observer does not need to continuously observe.

Still further, according to the present invention, since the contamination on the surface of the infrared sensor or the mirror can be monitored while comparing it with the infrared intensity of the reference value, the contamination on the surface of the sensor or the mirror can be accurately monitored and reliably removed. Yes, and at the same time, sensor sensitivity can be accurately monitored to detect sensor abnormalities.

In this case, since the infrared sensor or the sensor and the mirror can be housed in the housing, the sensor and the mirror can be easily accessed from outside the duct.

[Brief description of the drawings]

1 and 2 are a schematic side view and a schematic plan view showing an embodiment of a temperature monitoring device according to the present invention.
3 and 4 are diagrams showing two different examples of means for reciprocating a mirror in the temperature monitoring device, and FIG. 5 is a diagram showing another form of the mirror. FIG. 6 is a pattern diagram showing an example of a display screen of the infrared intensity in the temperature monitoring device according to the present invention, and FIGS.
FIG. 7C is a pattern diagram of the display screen which has been changed over time and shown for explaining the display screen. FIG. 8 is a view for explaining a display screen of infrared intensity in the fire detection device according to the present invention. 9 and 10 are diagrams for explaining one embodiment of the fire detecting device according to the present invention, and FIG. 11 is a diagram showing another example. FIG. 12 is a perspective view schematically showing a Jungstrom-type air preheater to which a fire detection device according to the present invention can be optimally attached. 13 and 14 are views for explaining a conventional fire detecting device, FIG. 15 is a diagram showing another example of the conventional fire detecting device, and FIG. 16 is another example of the infrared sensor. FIG. DESCRIPTION OF SYMBOLS 1 ... Rotor outer cylinder, 2 ... Partition plate, 3 ... Heating element, 14 ... Drive rod, 17 ... Air nozzle, 19
... Controller, 21 ... Infrared sensor, 22 ... Lens, 31, 31 '... Mirror, 33 ... Image processing device, 34 ...
Display, 36: Radiant plate, 37: Heater, 40: Water / detergent nozzle, 43: Drive wire.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mamoru Araoka 1-1, Akunoura-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Atsushi Iwanaga 1-1, Akunoura-cho, Nagasaki City, Nagasaki Prefecture Inside Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Akira Hashimoto 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Inventor Toshiyuki Takegawa 1-1-1, Akunoura-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries (72) Inventor: Yuichi Ide 1-1, Akunoura-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries: (72) Inventor: Yasuhiko Sato 1-1-1, Akunoura-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries (72) Inventor Shozo Kaneko 1-1, Akunouramachi, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (56) References JP-A-63-5251 (JP, A) JP-A-60-530 (JP, U) JP-A-59-30757 (JP, U) US Patent 3,730,259 (US, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) G01J 5/48

Claims (3)

(57) [Claims] 1. A rotary air preheater having a rotating rotor, which is disposed on a side of a preheated air inlet duct of a rotor body and linearly reciprocates around a heating element filled between partition plates for heating. A mirror for reflecting infrared rays emitted from the element, a sensor for detecting infrared rays emitted by the heating element and reflected by the mirror, and image processing using detection output of the sensor as information to obtain a temperature of the heating element; A device for displaying information corresponding to the position of the mirror, and a sensor or the sensor and the mirror are provided in a housing in which the sensor and the mirror are housed so as to face the sensor or the mirror, and emit infrared light of a constant intensity. Means, and comparing a detection value obtained by detecting infrared rays emitted from the means with the sensor with a reference value. Means, means for cleaning the surface of the sensor or the mirror when the detection value is lower than a reference value, detection value and reference value of infrared light emitted from means for emitting infrared light of a constant intensity after the cleaning. And a means for comparing again with each other to determine the presence or absence of an abnormality in the sensor. 2. A fire detector according to claim 1, wherein said linearly reciprocating mirror is a mirror in the form of a concave mirror. 3. A fire detecting device for a rotary air preheater according to claim 1, wherein said sensor or means for cleaning the surface of said mirror uses air, water and a detergent singly or in combination. .