JP2002022548A - Probe for continuous temperature measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe for continuous temperature measurement used in a furnace having a chemically, thermally, and mechanically severe environment such as an incinerator in a waste incineration plant. SOLUTION: This probe for continuous temperature measurement is made by inserting a thermocouple into a heat-resistant protection tube with a closure part on its end part and causing a hot contact part of the thermocouple to face to the inside of the closure part, The closure part comprises a heat-resistant partition transversely separating an internal space of the protection tube leaving a cavity part in the end of the protection tube and a heat-resistant filler for gas invasion prevention packed in the cavity part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous temperature measuring probe used in a furnace in an extremely harsh environment chemically, thermally and mechanically, such as an incinerator in a cleaning plant.

[0002]

2. Description of the Related Art Conventionally, there has been known a continuous temperature measuring probe in which a thermocouple is inserted into a heat-resistant protective tube provided with a closed portion at the tip and a hot junction portion of the thermocouple faces the inside of the closed portion. The protection tube is made of stainless steel such as SUS310, 304, 316, sandvik P-4 (Cr type), Inconel (Ni-Cr), etc. in order to enable use in a high temperature environment such as a blast furnace or a heating furnace. Formed of a metal tube. However, it was confirmed that when such a continuous temperature measuring probe was used in an incinerator or the like in an incineration plant, the heat-resistant protective tube would bend down in a short time and would not withstand use. This is because the inside of such an incinerator is at an extremely high temperature, has very strong oxidizing and sulfidizing properties, and is in a very severe environment chemically, thermally and mechanically.

The purpose of preventing the protection tube from being bent at the time of continuous temperature measurement can be achieved by forming the protection tube from an oxide dispersion strengthened heat-resistant alloy. Such an oxide dispersion-strengthened heat-resistant alloy contains 10 to 40% by weight of Cr, 10% by weight or less of Al, 5% by weight or less of Ti, 0.1 to 2% by weight of a high melting point metal oxide, and the balance. Is substantially Fe
It satisfies high temperature heat resistance, high temperature corrosion resistance and mechanical strength. Therefore, if a protective tube for a continuous temperature measuring probe is manufactured using this oxide dispersion strengthened heat-resistant alloy, the results of an experiment in an incinerator in an oxidizing atmosphere heated to 1320 ° C. show that the tube is completely deformed even after 168 hours. It is reported that there is no oxidation and the oxidation amount is small. An oxide dispersion strengthened heat-resistant alloy is commercially available, for example, under the product name of MA956.

[0004]

When a protective tube used for a continuous temperature measuring probe is made of a tube made of a heat-resistant alloy of the oxide dispersion strengthened type as described above, the tip of the tube must be securely closed. Must. In this regard, a technique is known in which a bottom wall portion is formed by squeezing a distal end portion of a pipe material to leave a small hole at the center portion and swell, and then close the small hole by welding.

[0005] However, since the end of a pipe made of a heat-resistant alloy of an oxide dispersion strengthened type is drawn and then a protective tube in which the small hole at the end is sealed by welding is used as a continuous temperature measuring probe, a severe furnace environment is required. It has been found that when exposed to a long time, the weld metal peels off and falls off from the small holes. The reason is that, when the small hole at the tip is sealed by welding, the components Y ₂ O ₃ and Al
Is eluted on the surface, and the internal components are reduced, resulting in insufficient strength. That is, Y ₂ O ₃ is added to improve the high-temperature strength, but when it is subjected to the welding temperature, it disturbs the dispersion in the alloy, and is considered to lower the high-temperature strength.

The applicant of the present application has disclosed a joint application in Japanese Patent Application No. 10-235006 in which, when a small hole left in the center portion is closed by drawing a front end portion of a pipe material, Fe containing Fe containing Co is used. -We have learned a technique of filling and welding the small holes with a welding metal made of a Cr-based alloy and a low-carbon heat-resistant alloy, but the sealing effect of the welding metal is still insufficient.

If, during continuous temperature measurement, the weld metal is separated from the small holes and the gas inside the furnace enters the protective tube, the thermocouple may be deteriorated, or in the worst case, the gas outside the furnace may be removed from the protective tube. There is a danger that the gas will be ejected from the terminal box toward the worker through the terminal box.

[0008]

According to the present invention, there is provided a method for manufacturing a protection tube for a continuous temperature measuring probe by using a tube made of a heat-resistant alloy of an oxide dispersion strengthened type. Providing a heat-resistant partition wall that cuts off the internal space of the tube material transversely, leaving a hollow portion at the tip of the tube material,
The partition is welded to the inner surface of the tube. According to this, the welded portion is located deep inside from the tip of the tube material without being exposed to the outside of the tube material, so that it is suitably protected from the severe atmosphere in the furnace. Moreover, since the partition wall itself is provided at a deeper position inside the tip of the pipe material,
It does not fall off easily. In addition, the welding work of the partition wall
It can be easily performed through the cavity. And since the cavity is filled with a heat-resistant gas intrusion prevention filler,
Even when a gap is formed in the welded portion between the partition wall and the pipe, it is possible to reliably prevent the gas in the furnace from entering the thermocouple.

By the way, according to the above configuration, the hot junction at the tip of the thermocouple inserted into the protection tube faces the position retracted from the tip of the protection tube corresponding to the position of the partition wall. However, according to the present invention, the protective tube is filled with a heat conductive filler made of refractory powder for embedding the tip of the thermocouple. By doing so, the temperature measurement response time of the thermocouple was able to be secured in a short time equivalent to or longer than the conventional one.

Therefore, the present invention is configured as a first means in that a thermocouple is inserted into a heat-resistant protective tube having a closed portion at a tip end, and a hot junction portion of the thermocouple is placed inside the closed portion. In the continuous temperature measuring probe, the closed part is filled with the heat-resistant partition wall that cuts off the inner space of the protective tube while leaving a hollow part at the tip of the protective tube, and is filled in the hollow part. And a heat resistant gas intrusion preventing filler.

Further, the present invention is configured as a second means in that a thermocouple is inserted into a heat-resistant protective tube having a closed portion at a tip portion, and a hot junction portion of the thermocouple is placed inside the closed portion. In the continuous temperature measuring probe, the closed part is filled with the heat-resistant partition wall that cuts off the inner space of the protective tube while leaving a hollow part at the tip of the protective tube, and is filled in the hollow part. The protective tube is filled with a heat conductive filler made of a refractory powder for embedding the tip of a thermocouple located near the partition wall. On the point.

In an embodiment of the present invention, the partition wall has a portion facing the hollow portion welded to the inner surface of the protective tube.

The protective tube and the partition wall are preferably made of an oxide dispersion strengthened heat-resistant alloy, and the gas intrusion preventing filler is preferably selected from one or more of a refractory cement and a refractory adhesive.

The heat conductive filler in the second means is as follows:
It is preferably selected from one or more of alumina, zirconia, silica and magnesia.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

(Overall Configuration) FIG. 1 shows the whole of a continuous temperature measuring probe. In the illustrated example, a heat-resistant protective tube 1 is shown.
Is divided into a tail-end side protection tube 1a having a terminal box 2 at the tail end and a flange 3 in the middle part in the axial direction, and a front-end side protection tube 1b having a closing portion 4 at the front end. 1a,
1b is concentrically connected by a joint 5. However, the protective tube 1 may be integrally formed of a single tube without being divided as in the illustrated example.

The protective tube 1 is made of a heat-resistant alloy of the oxide dispersion strengthened type, and can withstand a long time without sagging bending at the time of continuous temperature measurement. For example, 1320
Even when used in an incinerator in an oxidizing atmosphere heated to a degree C, there was no deformation even after 168 hours, and the amount of oxidation was small. The oxide dispersion strengthened heat-resistant alloy contains 10 to 40% by weight of Cr, 10% by weight or less of Al, 5% by weight or less of Ti, and 0.1 to 10% by weight of a high melting point metal oxide.
2% by weight, with the balance being substantially Fe, satisfying high-temperature heat resistance, high-temperature corrosion resistance and mechanical strength. Specifically, for example, an oxide dispersion strengthened heat-resistant alloy commercially available under the product name of MA956 can be used. As shown in the figure, the protection tube 1 is divided into a tail-side protection tube 1a and a tip-side protection tube 1.
b, the protective tubes 1a and 1b may be formed of an oxide dispersion-strengthened heat-resistant alloy, but at least the distal protection tube 1b may be formed of an oxide dispersion-strengthened heat-resistant alloy. good.

A sheath thermocouple 6 is housed in the protective tube 1, and the hot junction 7 of the thermocouple 6 faces the inside of the closed portion 4. Although not shown, the sheath thermocouple 6 is inserted into an insulating sheath formed by arranging short cylindrical insulators in the axial direction, and constitutes a known sheath thermocouple.

As shown in FIG. 2, such a continuous temperature measuring probe is inserted into a temperature measuring opening provided through a furnace wall W of an incinerator or the like, and a flange 3 is attached to an outer surface of the furnace wall. By attaching and fixing, the distal end region of the protective tube 1 (the distal-side protective tube 1b in the illustrated example) extends into the furnace, and the temperature sensed by the hot junction 7 of the thermocouple 6 is continuously measured. .

(Structure of Closed Portion) As shown in FIG. 2 (A), the closed portion 4 has a heat-resistant portion that cuts off the inner space of the protective tube 1 while leaving a cavity S at the tip of the protective tube 1. And a heat-resistant gas intrusion preventing filler 9 filled in the cavity S. Specifically, protection tube 1
(In the illustrated example, the distal protective tube 1b in the drawing) inserts a disk-shaped partition wall 8 from the distal end of the tubular material into the tubular material and fixes it by fitting or spot welding to narrow the distal end of the tubular material. After forming the diaphragm wall 11 bent inward leaving the opening hole 10 at the center by processing, the partition plate 8 is welded 12 to the inner surface of the pipe at the position leaving the cavity S. The work for this welding 12 can be easily performed from the opening hole 10 through the cavity S, and therefore, the partition wall 8
Is welded to the inner surface of the pipe material.
Next, the cavity S is filled with the heat-resistant gas intrusion preventing filler 9 through the opening hole 10. After the gas intrusion prevention filler 9 has been filled in the hollow portion S, it keeps high airtightness in a solidified state. Since the opening S of the cavity S is narrowed by the diaphragm wall 11, the gas intrusion preventing filler 9 does not fall out of the opening 10.

The partition wall 8 is formed in a disk shape from the same oxide dispersion strengthened heat-resistant alloy as the protective tube 1. The welding 12 of the partition wall 8 may be based on a filling welding technique proposed by Japanese Patent Application No. 10-235006, which is a Fe-Cr alloy containing Co and uses a low-carbon heat-resistant alloy as a welding metal. And other known welding techniques.

The gas intrusion preventing filler 9 can be selected from one or more of a refractory cement and a refractory adhesive. For example, it may be composed of one of the refractory cement and the refractory adhesive, but a composite layer of the refractory cement and the refractory adhesive may be formed inside the cavity S.

(Structure of Thermal Conductive Filler) In the preferred embodiment shown in FIG. 2A, the tip of the thermocouple 6 located near the partition wall 8 is attached to the protection tube 1 (tip protection tube 1b). It is embedded and held in a heat conductive filler 13 made of the filled refractory powder. The heat conductive filler 13 may be a refractory powder and a material having good heat conductivity.
It can be selected from one or more of zirconia, silica and magnesia. For example, it may be composed of any one of alumina, zirconia, silica, and magnesia, or may be composed of a selected mixed powder thereof. As will be described later, the heat conductive filler 13 is for the purpose of ensuring the response of the thermocouple 6 at the time of temperature measurement. Therefore, the heat conductive filler 13 may be filled over the entire length of the protection tube 1 (tip side protection tube 1b). It is sufficient to fill only a limited area extending from the pair of hot junctions 7 by a predetermined length.

(Two Embodiments of the Present Invention) The continuous temperature measuring probe according to the first embodiment shown in FIG. 2A is provided with the heat conductive filler 13 as described above. The continuous temperature measuring probe according to the second embodiment shown in FIG. 2B does not have this. Other configurations are the same.
Then, when a comparison experiment of the response speed was performed using the continuous temperature measurement probe based on these two embodiments, the second embodiment showed that the response time (the time until equilibrium of the electromotive force of the thermocouple) was obtained. In contrast, the first embodiment requires only 72 seconds, whereas the first embodiment requires only 72 seconds.

[0025]

According to the present invention, in order to form the heat-resistant protective tube 1 in the continuous temperature measuring probe, when the tip of the tube is securely closed, the hollow S is left at the tip of the tube. Since the heat-resistant partition wall 8 that blocks the internal space transversely is fixed, the welding portion 12 between the partition wall 8 and the pipe material (protective tube 1) is not exposed to the outside of the protective tube 1 without being welded. Since it is located deep inside the protective tube 1 from the tip, it is suitably protected from the severe atmosphere in the furnace and does not cause welding delamination. In addition, the partition wall 8 itself is also provided at a position deep inside the tip of the protection tube 1, and furthermore, the cavity S
Is filled with the filler 9, so that the partition wall 8 does not fall out of the protective tube 1. Since the filler filled in the cavity S constitutes the heat-resistant and highly airtight gas intrusion preventing filler 9, a gap is formed in the welded portion 12 between the partition wall 8 and the protective tube 1. Even in such a case, it is possible to reliably prevent the in-furnace gas from invading the thermocouple 6, thereby enabling long-term continuous temperature measurement.

Further, according to such a configuration, the partition wall 8
The hot junction 7 at the tip of the thermocouple 6 inserted into the protection tube 1 is positioned at a position retracted from the tip of the protection tube 1 corresponding to the position of the thermocouple 6, so that the temperature measurement response time of the thermocouple 6 However, according to the present invention, the heat conductive filler 13 made of a refractory powder for embedding the tip of the thermocouple 6 can be used.
Is filled in the protective tube 1, so that there is an effect that the temperature measurement response time of the thermocouple 6 can be secured in a short time equal to or longer than the conventional one.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a continuous temperature measuring probe of the present invention.

FIG. 2 shows an embodiment of the present invention in an enlarged manner, and (A)
FIG. 2 is a cross-sectional view illustrating a first embodiment, and FIG. 2B is a cross-sectional view illustrating a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat-resistant protective tube 4 Closed part 6 Thermocouple 7 Hot junction part 8 Partition wall 9 Heat-resistant gas intrusion prevention filler 10 Opening hole 11 Restricted wall 12 Welding 13 Heat conductive filler made of refractory powder S Cavity

Claims (6)

[Claims] 1. A continuous temperature measuring probe comprising a thermocouple inserted into a heat-resistant protective tube having a closed portion at a distal end, and a hot junction portion of the thermocouple facing the inside of the closed portion. Is composed of a heat-resistant partition wall that leaves a hollow portion at the tip of the protective tube and cuts off across the internal space of the protective tube, and a heat-resistant gas intrusion preventing filler filled in the hollow portion. A continuous temperature measuring probe characterized by comprising: 2. A continuous temperature measuring probe in which a thermocouple is inserted into a heat-resistant protective tube having a closed portion at a distal end thereof, and a hot junction of the thermocouple faces the inside of the closed portion. Is composed of a heat-resistant partition wall that leaves a hollow portion at the tip of the protective tube and cuts off across the internal space of the protective tube, and a heat-resistant gas intrusion preventing filler filled in the hollow portion. A continuous temperature measuring probe characterized in that a protective tube is filled with a heat conductive filler made of refractory powder for embedding a tip portion of a thermocouple located near the partition wall. 3. The continuous temperature measuring probe according to claim 1, wherein a portion facing the hollow portion of the partition wall is welded to an inner surface of the protection tube. 4. The continuous temperature measuring probe according to claim 1, wherein the protective tube and the partition wall are made of an oxide dispersion strengthened heat-resistant alloy. 5. The continuous temperature measuring probe according to claim 1, wherein the gas intrusion preventing filler is selected from one or more of a refractory cement and a refractory adhesive. 6. The continuous temperature measuring probe according to claim 2, wherein the thermal conductive filler is selected from one or more of alumina, zirconia, silica, and magnesia.