JP6578890B2 - Airtight joint and heat treatment method using airtight joint - Google Patents

Description

  The present invention relates to an airtight joint and a heat treatment method using the airtight joint.

  A seal structure of a pipe connection part in a high temperature state is known. As such a seal structure, for example, in Patent Document 1, the heat-resistant cylindrical body is sandwiched from both sides so as to slightly overlap in the axial direction between the metal inlet core tube and the outlet core tube, and is attached to at least one end portion. A structure is described in which a heat-resistant cylindrical body is supported flexibly and airtightly via a flexible ring fitted inside a fixed sleeve.

Japanese Utility Model Publication No. 61-27094

  In a joint that closes the opening at the end of the core tube in a heating furnace, when the core tube becomes hot, the gap between the core tube and the joint is large due to the difference in thermal expansion coefficient between the core tube and the joint. Changes. For this reason, it is conceivable to apply a conventional seal structure for a pipe connection portion in a high temperature state. However, for example, in the structure described in Patent Document 1, the heat-resistant cylindrical body and the metal inlet core tube (or the outlet core tube) are only sandwiched so as to slightly overlap in the axial direction. Since there is no sealing member, the airtightness between them cannot be taken.

  Therefore, an object of the present invention is to use a hermetic joint and a hermetic joint that can reliably keep hermeticity even when the core tube reaches a high temperature in a joint that closes the opening at the end of the core tube in a heating furnace. It is to provide a heat treatment method.

An airtight joint according to one aspect of the present invention is an airtight joint that closes an opening at an end of a core tube in a heating furnace,
An airtight joint body having a holding portion sandwiched between the inner peripheral surface and the outer peripheral surface of the furnace core tube and provided with a groove on the inner peripheral surface side, and fitted into the groove of the holding portion and in contact with the inner peripheral surface. Has one O-ring,
The linear expansion coefficient of the holding part is larger than the linear expansion coefficient of the core tube,
The first O-ring is pressed against the inner peripheral surface when the holding portion expands by heating and is sealed ,
A second O-ring and a sleeve adjacent to the second O-ring between the hermetic joint body and the outer peripheral surface of the core tube;
Furthermore, it has a tightening member disposed outside the airtight joint body,
By tightening the airtight joint main body with the tightening member, a space between the outer peripheral surface of the core tube and the airtight joint main body is sealed by the second O-ring.

  A heat treatment method according to one embodiment of the present invention uses the above-described hermetic joint in a heating furnace that performs heat treatment by flowing a gas containing a corrosive gas into a furnace core tube.

  According to the present invention, in a joint that closes the opening at the end of the core tube in the heating furnace, airtightness can be reliably maintained even when the core tube becomes hot.

It is a schematic block diagram which shows an example of the heating furnace which uses the airtight coupling which concerns on this embodiment. It is sectional drawing of the airtight coupling which concerns on this embodiment in the state connected to the core tube of the heating furnace of FIG.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.
The hermetic joint according to the embodiment of the present invention,
(1) An airtight joint that closes an opening at an end of a core tube in a heating furnace,
An airtight joint body having a holding portion sandwiched between the inner peripheral surface and the outer peripheral surface of the furnace core tube and provided with a groove on the inner peripheral surface side, and fitted into the groove of the holding portion and in contact with the inner peripheral surface. Has one O-ring,
The linear expansion coefficient of the holding part is larger than the linear expansion coefficient of the core tube,
The first O-ring is pressed against the inner peripheral surface when the holding portion expands by heating and is sealed ,
A second O-ring and a sleeve adjacent to the second O-ring between the hermetic joint body and the outer peripheral surface of the core tube;
Furthermore, it has a tightening member disposed outside the airtight joint body,
By tightening the airtight joint main body with the tightening member, a space between the outer peripheral surface of the core tube and the airtight joint main body is sealed by the second O-ring.
In the airtight joint of (1) above, when the temperature of the core tube is increased by heating, since the linear expansion coefficient of the holding portion is larger than the linear expansion coefficient of the core tube, the holding portion is on the outer side than the core tube expands outward. The degree of expansion is large. Thereby, since the first O-ring is pressed against the inner peripheral surface of the core tube and sealed, the airtightness between the core tube and the airtight joint can be reliably maintained.

In addition, the hermetic joint ( 1 ) can seal the space between the outer peripheral surface of the core tube and the hermetic joint body with the second O-ring by tightening the hermetic joint body with the fastening member.

( 2 ) The material of the hermetic joint body is PTFE, and the material of the furnace core tube is quartz or alumina .
The airtight joint of ( 2 ) is excellent in heat resistance and corrosion resistance because the material of the airtight joint body is PTFE (abbreviation of polytetrafluoroethylene). Further, if the material of the core tube is quartz or alumina , a core tube having a wide size range from a small size to a large size can be manufactured.

The heat treatment method using the airtight joint according to the embodiment of the present invention,
( 3 ) In the heating furnace that performs heat treatment by flowing a gas containing a corrosive gas into the furnace core tube, the hermetic joint of (1) or (2) is used.
The heat treatment method of ( 3 ) described above ensures that airtightness with the airtight joint is ensured even when the core tube becomes hot in a heating furnace in which a gas containing corrosive gas is flowed into the core tube and heat treatment is performed. Can keep.

[Details of the embodiment of the present invention]
Specific examples of the airtight joint and the heat treatment method using the airtight joint according to the embodiment of the present invention will be described below with reference to the drawings.
In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

FIG. 1 is a schematic configuration diagram illustrating an example of a heating furnace 10 using an airtight joint 1 according to the present embodiment. FIG. 2 is a cross-sectional view of the hermetic joint 1 according to this embodiment in a state where it is connected to the core tube 2 of the heating furnace 10 of FIG.
The heating furnace 10 using the hermetic joint 1 illustrated in FIG. 1 is an externally heated rotary furnace (for example, a rotary kiln or the like) that heats an inner heating target while rotating the furnace core tube 2. The heating furnace 10 includes an airtight joint 1, a furnace core tube 2, a heater 3, a gas exhaust part 4, a gas supply pipe 5, a gas exhaust pipe 6, a rotation mechanism part 7, rotary joints 8 a and 8 b.

  The core tube 2 is installed in the horizontal direction in the heating furnace 10, and a heater 3 is installed outside the core tube 2 so as to surround the core tube 2. The core tube 2 is a cylindrical body made of a material such as alumina, quartz, or carbon. The gas in the heating furnace 10 is exhausted from the gas exhaust unit 4.

  Airtight joints 1 are provided at both axial ends of the core tube 2. In the heating furnace 10, rotation mechanism portions 7 are provided around the outer peripheral surface of the furnace core tube 2 on the inner side in the axial direction from the hermetic joint 1. The rotation mechanism unit 7 transmits the rotation of the motor 7 a to the core tube 2.

  A gas supply pipe 5 is connected to one airtight joint 1 via a rotary joint 8a, and a gas discharge pipe 6 is connected to the other airtight joint 1 via a rotary joint 8b. The gas supply pipe 5 and the gas discharge pipe 6 are prevented from rotating by the rotary joints 8a and 8b.

  As shown in FIG. 2, the airtight joint 1 is a joint that is attached so as to keep the airtightness by closing the opening 2 a at the end of the core tube 2. The hermetic joint 1 is provided with a hermetic joint body 11 so as to close the opening 2 a at the end of the core tube 2 and sandwich the inner peripheral surface and outer peripheral surface of the end of the core tube 2.

  The airtight joint body 11 has a holding portion 11c provided with two grooves 11b in the example of FIG. 2 on a surface 11a facing the inner peripheral surface of the end portion of the core tube 2. The hermetic joint body 11 includes a first O-ring 12 that fits into the groove 11b of the holding portion 11c and contacts the inner peripheral surface of the core tube 2. As the material of the first O-ring 12, for example, fluorine rubber or the like is used. Fluoro rubber has corrosion resistance and is relatively inexpensive.

  At least the holding portion 11 c of the hermetic joint body 11 is formed of a material whose linear expansion coefficient is larger than that of the core tube 2. For example, examples of the material of the holding portion 11c include a fluororesin (for example, PTFE, PFA (perfluoroalkoxyalkane), ETFE (ethylene / tetrafluoroethylene copolymer), etc.). A fluororesin is preferred because of its good heat resistance and corrosion resistance. Among the above fluororesins, PTFE has further good processability. In the example shown in FIG. 1, the holding part 11c is provided integrally with the hermetic joint body 11, and the whole of the hermetic joint body 11 is made of the same material as the holding part 11c. However, the holding part 11c may be formed separately from the airtight joint body 11.

  As described above, the linear expansion coefficient of the holding portion 11 c is larger than the linear expansion coefficient of the core tube 2. Therefore, when the core tube 2 is heated by the heater 3, the expansion amount in the radial direction of the holding portion 11c is larger than the expansion amount of the core tube 2, and the first O-ring fitted into the groove 11b of the holding portion 11c. 12 is pressed against the inner peripheral surface of the core tube 2 and crushed. Thereby, it can seal so that the clearance gap between the internal peripheral surface of the core tube 2 and the airtight coupling main body 11 may be plugged up.

  The hermetic joint 1 includes a second O-ring 13 and a sleeve 14 adjacent to the second O-ring 13 between the hermetic joint body 11 and the outer peripheral surface of the core tube 2. In the example of FIG. 2, a plurality (three each) of second O-rings 13 and sleeves 14 are provided alternately adjacent to each other. As the material of the second O-ring 13, for example, fluorine rubber or the like is used in the same manner as the first O-ring 12.

  Further, the airtight joint 1 includes a joint cap 15 as a fastening member that is fitted and tightened on the outer periphery of the airtight joint body 11. As shown in FIG. 2, the second O-ring 13 is pressed and crushed by fitting the joint cap 15 to the outer periphery of the airtight joint body 11 and pushing it in the axial direction. Thereby, it can seal so that the clearance gap between the outer peripheral surface of the core tube 2 and the airtight coupling main body 11 may be plugged up. In addition, a screw thread may be provided on the inner periphery of the joint cap 15 and the outer periphery of the airtight joint body 11 so as to be screwed together.

Hereinafter, the heat processing method which uses the airtight coupling 1 which concerns on this embodiment is demonstrated.
First, either one of the airtight joints 1 is removed from the end of the core tube 2, and a substance to be heat-treated is put into the core tube 2 and placed in the reaction unit 9.
Next, in a room temperature environment, the removed airtight joint 1 is attached so as to close the opening 2 a at the end of the core tube 2, and the joint cap 15 is fitted into the outer periphery of the airtight joint body 11 and pushed in.

Next, a gas containing a corrosive gas for causing a predetermined chemical reaction to occur on the substance placed in the reaction unit 9 is supplied from the gas supply pipe 5 at a predetermined flow rate. The gas used in the chemical reaction is discharged from the gas discharge pipe 6 so as to keep the gas pressure inside the core tube 2 at a predetermined value. In addition, the inside of the core tube 2 is heated by the heater 3 so as to have a temperature suitable for the chemical reaction, and the motor 7 a is started to rotate the core tube 2 by the rotation mechanism unit 7. Thereby, a predetermined chemical reaction proceeds in the reaction unit 9.
After the chemical reaction is completed, the gas supply from the gas supply pipe 5 is stopped.

  In the heat treatment method using the hermetic joint 1 according to the above-described embodiment, when the core tube 2 becomes high temperature in the heating furnace 10 that performs heat treatment by flowing a gas containing a corrosive gas into the core tube 2. The degree to which the holding portion 11c expands outward is greater than the furnace core tube 2 expands outward. As a result, the first O-ring 12 is pressed against the inner peripheral surface of the core tube 2 and sealed, so that the core tube 2 and the airtight joint 1 can be reliably kept airtight.

(Example)
Hereinafter, in the heating furnace 10, the airtightness between the core tube 2 and the airtight joint during the heat treatment in the case where the airtight joint of the example is used and the case where the airtight joint of the comparative example is used was compared.
The hermetic joint of the example is the hermetic joint 1 of the present embodiment.
The hermetic joint of the comparative example is a hermetic joint having a structure that is different from the hermetic joint 1 of the present embodiment only in that the holding portion 11c and the first O-ring (airtight holding structure inside the hermetic joint 1) are not provided.

For the core tubes used in the examples and comparative examples, those having a material of alumina (Al ₂ O ₃ ) and those having a material of quartz were prepared. Furthermore, three types of core tubes (outer diameters: φ145 mm, φ40 mm, and φ30 mm) having different outer diameters were prepared as the core tubes made of each material. The linear expansion coefficient of alumina (Al ₂ O ₃ ) is 7.2 × 10 ⁻⁶ , and the linear expansion coefficient of quartz is 5.5 × 10 ⁻⁷ . In this measurement, a carbon core tube was not used, but the linear expansion coefficient of carbon is 2 × 10 ⁻⁶ .

In addition, the hermetic joint of the example and the comparative example is made of PTFE, and in the example, the holding part 11c and the hermetic joint body 11 are integrally provided (that is, the holding part). 11c is PTFE). PTFE has a linear expansion coefficient of 10 × 10 ⁻⁵ .

That is, six types of core tubes are prepared as described above, and the airtight joint of the example or comparative example is attached to each core tube, and the heating furnace 10 is set to a predetermined one based on the heat treatment method of the present embodiment described above. It heated on heating conditions, the expansion amount of the core tube and the airtight joint was measured, and it was investigated whether the gas leak occurred between the core tube and the airtight joint as a measurement of airtightness. The heating conditions are as follows: Heating condition 1: When heating from room temperature (20 ° C.) to 100 ° C.
Heating condition 2: Two types were used when heated from room temperature (20 ° C.) to 200 ° C.
Table 1 shows the measurement results when the material of the core tube is alumina (Al ₂ O ₃ ), and Table 2 shows the measurement results when the material of the core tube is quartz. In Tables 1 and 2, the result of the airtightness is indicated as “X” when it is recognized that a leak has occurred, and “◯” when it is not recognized that a leak has occurred.

As shown in Tables 1 and 2, there was no difference in the airtight result between the case where the material of the core tube was alumina (Al ₂ O ₃ ) and the case where the material of the core tube was quartz. In this measurement, a carbon core tube was not used, but the linear expansion coefficient of carbon is a value between alumina (Al ₂ O ₃ ) and quartz, and the result of airtightness is the same. it is conceivable that.
When the hermetic joint 1 of the example was used, the evaluation was “◯” in all cases, and no leak was observed, and the hermeticity was maintained.
In contrast, when the hermetic joint of the comparative example was used for a core tube having an outer diameter of φ145 mm, occurrence of leakage was observed in heating conditions 1 and 2. Further, when the hermetic joint of the comparative example was used for a core tube having an outer diameter of φ40 mm, occurrence of leakage was observed under heating condition 2. In addition, when the hermetic joint of the comparative example was used for a core tube having an outer diameter of φ30 mm, no leakage was observed in the heating conditions 1 and 2.

Since the linear expansion coefficient of the hermetic joint is larger than the linear expansion coefficient of the core tube, the expansion amount of the inner diameter of the hermetic joint is larger than that of the outer diameter of the core tube during heating. A gap between the outer peripheral surface and the inner peripheral surface of the airtight joint is increased.
In the comparative example, when the O-ring (second O-ring 13) that closes the gap between the outer peripheral surface of the core tube and the inner peripheral surface of the hermetic joint is at room temperature (20 ° C.), the collapse amount shown in Table 3 is obtained. If this is the case, the gap can be closed if the gap is within the range of the amount of crushing even if the gap becomes high. However, if this gap exceeds the above-mentioned crushing amount, the gap cannot be closed and a leak occurs.

Table 3 is a table showing the crushing amount (JIS B2401) of a standard O-ring made of fluororubber.
In the comparative example, in the case where leakage was found in the results of Tables 1 and 2, the difference between the expansion amount of the inner diameter of the airtight joint and the expansion amount of the outer diameter of the core tube was that of the O-ring (second O-ring 13). The amount of crushing (one side crushing amount in Table 3) is exceeded, and it is considered that leakage occurred from the gap between the outer peripheral surface of the core tube and the inner peripheral surface of the airtight joint.

  On the other hand, since the embodiment includes the holding portion 11c and the first O-ring 12 (the airtight holding structure inside the airtight joint 1), the expansion amount of the outer diameter of the holding portion 11c at a high temperature is The first O-ring 12 is pressed against the inner peripheral surface of the core tube 2 to be sealed, which is larger than the expansion amount of the inner diameter. Thereby, even if a gap is generated between the outer peripheral surface of the core tube 2 and the inner peripheral surface of the airtight joint 1, airtightness can be maintained.

In addition, the heat treatment method using the airtight joint and the airtight joint of the present invention is specifically for a reactor for reacting silicon carbide and chlorine described in, for example, Japanese Patent Application Laid-Open No. 2014-80325. Can be applied.
In the reaction furnace described in the above publication, the temperature in the furnace is heated to, for example, 1000 ° C. or more and 1300 ° C. or less, and a gas containing chlorine gas (corrosive gas) is supplied. It is made to react with the silicon carbide mounted on. In the reaction part, silicon carbide and chlorine react to produce silicon tetrachloride (SiCl ₄ ) and a porous carbon material (C). This reaction is represented by the following chemical formula (1).
SiC + 2Cl ₂ → SiCl ₄ + C (1)
That is, in the reactor described in the above publication, since a gas containing a corrosive gas (chlorine gas) flows in the high-temperature reaction part, it is necessary to reliably keep the joint part airtight. preferable.

DESCRIPTION OF SYMBOLS 1 Airtight joint 2 Furnace core tube 3 Heater 4 Gas exhaust part 5 Gas supply pipe 6 Gas exhaust pipe 7 Rotating mechanism part 7a Motor 8a, 8b Rotary joint 9 Reaction part 10 Heating furnace 11 Airtight joint main body 11a Inside of end part of core pipe 2 Surface facing the peripheral surface 11b Groove 11c Holding portion 12 First O-ring 13 Second O-ring 14 Sleeve 15 Joint cap (tightening member)

Claims (3)

An airtight joint that closes an opening at the end of a core tube in a heating furnace,
An airtight joint body having a holding portion sandwiched between the inner peripheral surface and the outer peripheral surface of the furnace core tube and provided with a groove on the inner peripheral surface side, and fitted into the groove of the holding portion and in contact with the inner peripheral surface. Has one O-ring,
The linear expansion coefficient of the holding part is larger than the linear expansion coefficient of the core tube,
The first O-ring is pressed against the inner peripheral surface when the holding portion expands by heating and is sealed ,
A second O-ring and a sleeve adjacent to the second O-ring between the hermetic joint body and the outer peripheral surface of the core tube;
Furthermore, it has a tightening member disposed outside the airtight joint body,
An airtight joint in which a space between the outer peripheral surface of the core tube and the airtight joint body is sealed by the second O-ring by fastening the airtight joint body with the tightening member. The hermetic joint according to claim 1, wherein the material of the hermetic joint body is PTFE, and the material of the furnace core tube is quartz or alumina. The heat processing method which uses the airtight coupling of Claim 1 or Claim 2 in the heating furnace which flows the gas containing corrosive gas in a furnace core tube, and heat-processes.

Images