JP3857421B2 - Can body overheating detection method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention , a vertical fin is provided between a water pipe adjacent to the periphery of a combustion chamber and a water pipe to form an inner and outer double annular water pipe wall, and an annular portion between both water pipe walls is used as a combustion gas passage. TECHNICAL FIELD The present invention relates to a can body overheat detection method and a can body overheat detection apparatus in a typical multi-tube once-through boiler . Specifically, the present invention relates to a can body overheat detection method and apparatus for quickly detecting the occurrence of an abnormal low water level accident such as overheating in the double annular multi-tube once-through boiler. Incidentally, the term "multi-tube once-through boiler" or "boiler" in the description of the following means "dual annular-tube once-through boiler" said unless otherwise specified.
[0002]
[Prior art]
If the multitubular once-through boiler is left unattended as a result of abnormally lowering the water level in the boiler due to any cause and overheating of the can body, a serious accident may occur. As a means for preventing such an accident, conventionally, as shown in FIG. 9, the outer side of the vertical fin 32 (combustion furnace) between the water pipe 31 and the adjacent water pipe and connected to the two water pipes in the axial direction. On the wall 35 side), a stud 34 having an insertion hole is fixed to hold the detection end of the temperature sensor 33, and the temperature sensor detection end 36 is inserted, and the temperature rise of the vertical fin 32 is constantly monitored. It was done to detect overheating of the body.
[0003]
[Problems to be solved by the invention]
Recently, however, as boilers have become more compact and restrictions on the mounting position have become greater, it has become difficult for temperature sensors to quickly detect the wall temperature of water pipes that would otherwise be most sensitive to heat. In other words, if the temperature sensor can be installed near the outlet of the combustion chamber where the heat load is high (in Fig. 2, the upper left side where there is no vertical fin on the inner ring side) , the response to overheating is fast, but the boiler is downsized. I couldn't find the space to install it. However, it was found that the conventional method for detecting overheating of cans cannot perform adequate functions at locations where the space between the water pipes that have a relatively large margin remains large but the heat load is relatively low. Thus, the present inventors have completed the present invention as a result of research aimed at providing means for detecting overheating of a can body that has a sufficient response speed even in a compact boiler.
[0004]
[Means for Solving the Problems]
Means for solving the problems will be described with reference to the drawings. The present invention provides a vertical fin 2 between the water pipe 1 and the water pipe 1 adjacent to the periphery of the combustion chamber to form an inner and outer double annular water pipe wall, and the annular portion between both water pipe walls is treated with combustion gas. A method for detecting overheating of a can in a double annular multi-tube once-through boiler as a passage, wherein a detection end insertion hole is provided from a proximal side 8 at a position away from the outlet of the combustion gas (that is, the inlet of the combustion gas passage). 7 studs 4 having a tip portion 9 which project provided, allowed to protrude independently tip portion 9 to the hand side 8 to the combustion furnace wall 5 side vertical fin 2 in penetrating the combustion gas stream 6 Fixed to the vertical fin 2, the temperature sensor detection end 10 is inserted into the detection end insertion hole 7, and the tip end portion 9 is maintained at a high temperature by the combustion gas and the hand portion 8 is maintained at a low temperature by the water pipe temperature via the vertical fin 2. is the temperature of the stud 4 during operation are measured, overheating of the can body by detecting the abnormal variation of the measured temperature A method for detecting overheating of a can body is provided. Preferably, in the method provided above, the position of the temperature sensor detection end 10 is set at an appropriate position between the outer side surface and the inner side surface of the vertical fin 2.
[0005]
A vertical fin 2 is provided between the water pipe 1 adjacent to the periphery of the combustion chamber and the water pipe 1 to form an inner and outer double annular water pipe wall, and the annular portion between the two water pipe walls serves as a combustion gas passage. An annular multi-tube type once-through boiler is a can body overheat detection device, and a stud 4 provided with a detection end insertion hole 7 from a hand side 8 at a position away from the outlet of the combustion gas vertically extends a tip portion 9. Through the fin 2 , it protrudes independently into the combustion gas flow 6 and is fixed to the vertical fin 2. During operation, the tip 9 is heated to a high temperature by the combustion gas 6, and the hand 8 is lowered by the water pipe 1 through the vertical fin 2. In order to measure the temperature of the stud 4 that is maintained at a temperature, a can body overheat detection device is provided that includes a temperature sensor having a detection end inserted into an insertion hole 7.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
A can body overheat detection method and apparatus according to the present invention will be specifically described with reference to the drawings showing an embodiment. FIG. 1 is a partially enlarged view of FIG. 2, and is a detailed view showing an example of the mounting configuration of the can body overheat detection device of the present invention, and FIG. 2 is a multi-tube type once-through flow showing the mounting position of the can body overheat detection device FIG. 3 is a sectional view in the direction perpendicular to the axis of the boiler, and FIG. 3 is a sectional view in the axial direction showing the main body structure of the can body overheat detection device of the present invention.
[0007]
In the can body overheat detection method of the present invention, the stud that holds the temperature sensor detection end is conventionally fixed to the outside of the vertical fin (filter wall side). A portion 9 is formed by protruding, a through hole is opened in the vertical fin 2, the tip portion 9 is penetrated, and the fuel gas 6 is protruded independently and fixed to the vertical fin 2. An insertion hole 7 for the temperature sensor detection end 10 is provided on the proximal side 8 of the stud 4 so that the detection end 10 is inserted and held.
[0008]
The shape of the stud 4 of the can overheating detection device of the present invention is not limited to the nail head shape as shown in the drawings, and can be determined as appropriate depending on the situation around the mounting position, the shape and sensitivity of the temperature sensor 3. The protrusion length from the inner surface of the vertical fin 2 and the diameter of the protruding portion are matters determined empirically to some extent depending on the type of the temperature sensor 3, the thickness of the vertical fin 2, and the mounting position. The length is 5 to 25 mm, and the diameter of the protruding portion 9 is 8 to 15 mm. On the other hand, an insertion hole 7 for inserting the temperature sensor detection end 10 is provided on the hand side 8, and the temperature sensor detection end 10 is inserted and held. Therefore, also in the present invention, the temperature sensor 3 measures the temperature in the insertion hole 7. Normally, the temperature sensor 3 has a detection end 10 at the tip, and is inserted into the bottom of the insertion hole 7 for measurement, so that the depth of the insertion hole 7 matches the temperature detection position. The measurement position is one of important matters in the present invention as described later. The stud 4 is attached to the vertical fin 2 by welding in order to make the heat conduction resistance as small as possible.
[0009]
The operation of the present invention will be described. In the can body overheat detection device of the present invention, during the operation of the boiler, the tip end portion 9 of the stud 4 protruding independently from the vertical fin 2 to the combustion gas side 6 is directly heated by the combustion gas. On the other hand, since the temperature of the water pipe 1 is considerably lower than the combustion gas temperature on the proximal side of the stud 4, it is cooled by the water pipe 1 through the vertical fin 2. The detected temperature is determined by the balance between heating and cooling at the measurement position. When an abnormality such as a low water level accident occurs and the water level of the boiler is lowered, for example, when the can body is overheated as exemplified by the temperature A of the water pipe facing the furnace in FIG. The temperature of the stud 4 rapidly rises as a whole due to the influence of the tip 9 heated at a high temperature, and the temperature sensor 3 detects the temperature rise as illustrated in FIG. A situation is detected. FIG. 4C shows the temperature detection state of the conventional temperature sensor.
[0010]
If the temperature sensor detection end is installed at an appropriate position, the temperature increase gradient and width are large, and an abnormal situation can be detected very easily and quickly. However, since the temperature at the tip end portion of the stud is considerably high even during normal operation, the position of the detection end 26 of the temperature sensor 23 is inserted too deeply into the tip end portion 25 of the stud 24 as illustrated in FIG. Even if an abnormality occurs, the temperature of the water pipe 21 rises due to the overheating of the can body, and the temperature of the tip portion 25 rises, the temperature sensor detection temperature D is the original temperature as shown in FIG. Even if the temperature A of the water pipe facing the furnace rises due to heating because of the high temperature, the temperature rise is small and tends to be difficult to detect. Therefore, the position of the temperature sensor detection end 10 is preferably a position that is close to the temperature of the water pipe 1 during normal operation and is easily heated by the combustion gas. This position is affected by the structure of the boiler, the mounting position and shape of the stud 4, the thickness of the vertical fin 2, etc., and it is sometimes necessary to adjust this, but in principle the vertical position as shown in FIG. Installed between the outer side of the fin and the inner side of the vertical fin as shown in (b).
[0011]
Although the temperature of the conventional can body overheat detection device is wide in the interval between the water pipes, the temperature when the heat can be mounted at a location where the heat load is relatively low is governed by the water pipe temperature for both heating and cooling, and the can body becomes overheated. However, since the temperature rises following the temperature of the water pipe, the rise width and gradient are small, and the detection of abnormal situations tends to be delayed.
[0012]
【Example】
Next, the effect of the can overheating detection method of the present invention was confirmed by comparison with the conventional method, and the result will be described. First, a multi-tube once-through boiler with dozens of water tubes, water tube length of 1 m, and maximum steam pressure of 10 kg / cm 2 was used to form a can with water tube spacing of 10 to 40 mm and vertical fin thickness of 5 to 10 mm. The can body overheat detection device of the present invention of the same type as shown in FIG. 1 was attached. Carbon steel is used for the stud of the can overheating detector of the present invention used, the tip is finished with a diameter of 10 mm and a length of 20 mm, and a detection end insertion hole with a diameter of 5.5 mm and a depth of 6 mm is formed on the hand side. Provided. The tip of this can body overheat detection device was inserted into an opening in the vertical fin, and 14 mm was projected from the inner surface into the combustion gas flow and welded to the outer surface side of the vertical fin. In order to detect the overheating state of the can body, a thermometer TC was attached at the position shown in FIG. 8 and the temperature of the water pipe facing the furnace was measured. In addition, in the conventional can body overheat detection device shown in FIG. 9, the tip portion was finished in a 10 × 10 × 30 mm block, and a detection end insertion hole having a diameter of 5.5 mm was provided. This was welded to the outer surface of the vertical fin.
[0013]
The measurement result in the overheated state of the can body is shown in FIG. A is the temperature measured in the water tube facing the furnace, B the temperature detected by the temperature sensor of the present invention embodiment, C is a detected temperature of the can body overheat detection equipment the conventional method. Furthermore, studs of the same type and size as those of the can body overheat detection device of the embodiment of the present invention were attached at the same positions. However, the depth of the sensor insertion hole was 21 mm, the tip of the sensor was inserted, and the response was measured. The results are shown in FIG. A is the temperature of the water pipe facing the furnace, and D is the detected temperature of the temperature sensor of this example.
[0014]
【The invention's effect】
By utilizing the can body overheat detection method and the apparatus of the present invention, it is possible to detect the overheat state quickly even if the detection end of the temperature sensor is placed around the water pipe with a small heat load, which was slow to detect in the conventional method. Became.
[Brief description of the drawings]
FIG. 1 is a detailed cross-sectional view showing an example of a mounting configuration of a can body overheat detection device according to the present invention. FIG. 2 is a cross-sectional view perpendicular to a boiler shaft showing a mounting position of the can body overheat detection device. FIG. 4 is a sectional view in the axial direction showing the main body structure of the can body overheat detection device. FIG. 4 is a record of the response state of each detection method in the overheat state of the can body. Cross-sectional view [Fig. 6] Response record for overheating when the detection end is too close to the tip. [Fig. 7] A diagram showing the range of the desired temperature sensor detection end. [Fig. 8] Temperature measurement of the furnace water pipe in the embodiment. FIG. 9 is a cross-sectional view showing an example of a mounting configuration of a conventional can body overheat detection device.
1: Water pipe 2: Vertical fin 3: Temperature sensor 4: Stud 5: Combustion furnace wall 6: Combustion gas flow 7: Detection end insertion hole 8: Hand side 9: Stud tip portion 10: Temperature sensor detection end 11: Temperature sensor Holder 12: Spring 21: Water pipe 22: Vertical fin 23: Temperature sensor 24: Stud 25: Stud tip portion 26 Temperature sensor detection end 31: Water pipe 32: Vertical fin 33: Temperature sensor 34: Stud 35: Combustion furnace wall 36: Temperature Sensor detection end TC: Thermometer

Claims (3)

Double annular multi-tube with a vertical fin between the water pipes adjacent to the periphery of the combustion chamber to form a double annular water pipe wall, with the annular part between the two water pipe walls as the combustion gas passage A method for detecting overheating of a can in a once-through boiler,
In a position away from the combustion gas outlet (i.e., the inlet of the combustion gas passage),
A stud having a tip portion that is provided with a detection end insertion hole from the proximal side and protrudes,
The proximal to the combustion furnace wall side vertical fin penetrates independently into the combustion gas stream is exiting can butt the tip portion, secured to the vertical fin,
The detecting end insertion hole by inserting a temperature sensor detecting end, the hot tip by combustion gas, hand portion with water tube temperature via a vertical fin to measure the temperature of the stud in operation is maintained at a low temperature ,
A method for detecting overheating of a can body, wherein an abnormal change in the measured temperature is detected to detect overheating of the can body.         The can body overheating detection method according to claim 1, wherein the temperature sensor detection end is installed between the outer side surface and the inner side surface of the vertical fin. Double annular multi-tube with a vertical fin between the water pipes adjacent to the periphery of the combustion chamber to form a double annular water pipe wall, with the annular part between the two water pipe walls as the combustion gas passage It is a can body overheat detection device in a once-through boiler,
A position apart from the outlet of the combustion gas, stud the detection end insertion holes provided from the proximal side, protrudes the tip portion of the vertical fin penetrates independently into the combustion gas stream, Re Tatehi Fixed to
During operation, in order to measure the temperature of the stud whose tip is kept at a high temperature by the combustion gas and whose hand is kept at a low temperature by the water pipe via the vertical fin, a temperature sensor having a detection end inserted into the insertion hole is used. can body overheat detection apparatus characterized by comprising.

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