JP5436542B2 - How to prevent damage to carbon reaction vessels - Google Patents

Description

  The present invention is a method for preventing a carbon reaction vessel in which a plurality of substantially cylindrical bodies made of carbon are connected from being damaged by thermal shock, and particularly a reaction for reacting tetrachlorosilane with hydrogen to convert it to trichlorosilane. The present invention relates to a method for preventing damage to a carbon reaction vessel used in a furnace.

Trichlorosilane (SiHCl ₃ ) is a special material gas used for manufacturing semiconductors, liquid crystal panels, solar cells, and the like. In recent years, demand has been steadily expanding, and growth is expected as a CVD material widely used in the electronics field.

Trichlorosilane is produced by contacting tetrachlorosilane (SiCl ₄ ) and hydrogen (H ₂ ) to achieve the following thermal equilibrium state.
SiCl ₄ + H ₂ ⇔SiHCl ₃ + HCl (1)
This reaction is performed by heating a source gas composed of gasified tetrachlorosilane and hydrogen to 700 to 1400 ° C. in a carbon reaction vessel accommodated in a reaction furnace.

  As a conventional carbon reaction vessel for producing trichlorosilane by the above reaction, for example, there is one described in Patent Document 1. This document proposes a carbon reaction vessel formed by stacking several substantially cylindrical bodies (substantially cylindrical objects) treated with a silicon carbide coating.

Japanese Patent No. 3529070

  The carbon reaction vessel for reacting tetrachlorosilane with hydrogen is preferably integrally molded to achieve excellent durability and heat transfer efficiency, but it is not suitable for use in production plants. Therefore, as proposed in Patent Document 1, a plurality of carbon substantially cylindrical bodies connected and integrated are used.

  In such a carbon reaction container, for example, as shown in FIG. 1, the inner diameter of the upper end of the substantially cylindrical body 101 is larger than the inner diameter of the body portion 104 in order to stably connect the substantially cylindrical bodies 101 made of carbon. The shoulder 102 is formed by the step generated by the difference in inner diameter between the upper end and the body portion 104. On the other hand, the outer diameter of the lower end of the substantially cylindrical body 101 is reduced from the outer diameter of the body portion 104. The protrusion 103 is formed by a step generated due to a difference in outer diameter with respect to 104. The shoulder 102 and the protrusion 103 are arranged so that when the substantially cylindrical bodies 101 are connected to each other, the protrusion 103 of one of the substantially cylindrical bodies 101 is fitted to the shoulder 102 of the other substantially cylindrical body 101. The depth of the portion 102 and the length of the protruding portion 103 are designed to be substantially the same. Further, in order to screw and fasten the substantially cylindrical bodies 101 to each other, a corresponding screw thread or screw groove (not shown) may be provided on the inner peripheral surface of the shoulder portion 102 and the outer peripheral surface of the protruding portion 103. .

However, since the substantially cylindrical body 101 having the above structure has the shoulder portion 102 and the protruding portion 103 at the upper end and the lower end thereof, the thickness at both ends is reduced to almost half of the body portion 104. As a result, the upper and lower end portions of the substantially cylindrical body 101 become structurally fragile.
In addition, since a plurality of substantially cylindrical bodies 101 are connected and integrated for use, if a sudden temperature change is applied, the protrusion 103 of one of the substantially cylindrical bodies and the shoulder 102 of the other substantially cylindrical body at the connecting portion. Due to the difference in thermal expansion or thermal shrinkage, the radial stress applied between the two changes. When this stress is remarkably increased, the thin shoulder portion 102 and the protruding portion 103 cannot withstand the load, causing cracks and cracks, which may damage the carbon reaction vessel 100.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for preventing a carbon reaction vessel in which a plurality of substantially cylindrical bodies made of carbon are connected from being damaged by thermal shock.

As a result of earnestly examining the method for solving the above problems, the present inventors have used a plurality of straight cylindrical substantially cylindrical bodies that do not have shoulders or protrusions, and the connecting parts between these substantially cylindrical bodies are on the outer peripheral side. From the above, it was found that by using a carbon ring, it is possible to suppress the occurrence of cracks in the connecting portion even when a carbon reaction vessel is used in a high heat environment.
However, even in this case, using the same material, even if it is a substantially cylindrical body that appears to be the same shape and size, the thermal expansion coefficient differs for each substantially cylindrical body, It has been found that depending on the combination order of the coupling, it may affect the cracking and airtightness of the carbon reaction vessel. In addition, since the carbon ring also thermally expands in the same manner as the substantially cylindrical body, depending on the difference in thermal expansion coefficient from the substantially cylindrical body to be fastened, cracks may occur in the connecting part or the airtightness may be affected. I found.

  Therefore, the present inventors have previously measured the thermal expansion coefficient of each substantially cylindrical body and ring, and the difference in thermal expansion coefficient between the upper end of one of the substantially cylindrical bodies and the lower end of the other substantially cylindrical body is determined. Arrange the cylinders in order of decreasing size, and fasten the cylinders with a ring that has a small difference in thermal expansion coefficient from the cylinders to prevent the carbon reaction vessel from being damaged by thermal shock. As a result, the inventors have found out that the present invention can be achieved.

  That is, the method for preventing breakage of a carbon reaction vessel according to the present invention comprises connecting a plurality of carbon substantially cylindrical bodies to a coefficient of thermal expansion at the upper end of one of the substantially cylindrical bodies connected to each other and the other substantially cylindrical body. The ends are butted together in an order that reduces the difference from the coefficient of thermal expansion at the lower end, and is arranged approximately coaxially. The butted ends are fastened with a carbon ring that has a small difference from the coefficient of thermal expansion of the cylindrical body. It is characterized by doing.

  By adopting such a configuration, the difference between the thermal expansion amount of one substantially cylindrical body and the thermal expansion amount of the other substantially cylindrical body can be reduced in each connecting portion, and any of the substantially cylindrical bodies can be reduced. Since the difference between the amount of thermal expansion and the amount of thermal expansion of the ring can also be reduced, an increase in stress applied to the connecting portion can be suppressed, and damage to the carbon reaction vessel can be prevented.

It is a schematic longitudinal cross-sectional view which shows the conventional carbon reaction container. It is a schematic longitudinal cross-sectional view which shows one form of the carbon-made reaction containers handled in this invention. It is a schematic perspective view which shows one form of the substantially cylindrical body handled in this invention. It is a schematic perspective view which shows one form of the ring handled in this invention.

1: carbon reaction vessel 2: substantially cylindrical body 3: ring 4: canopy 5: bottom plate 6: inlet port 7: outlet 8: connection upper end portion 9: connection lower end portion 100: carbon reaction vessel 101: substantially cylindrical body 102 : Shoulder part 103: Protruding part 104: Body part

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a method for preventing damage to a carbon reaction vessel used to generate a reaction product gas containing trichlorosilane and hydrogen chloride from a raw material gas containing tetrachlorosilane and hydrogen will be described.

As shown in FIG. 2, the carbon reaction vessel 1 handled in the present embodiment has a plurality of carbon-made substantially cylindrical bodies 2 that are arranged substantially vertically coaxially with their ends abutted to each other. It is configured by screwing and fastening the part with a carbon ring 3 from the outside.
The substantially cylindrical body arranged at the uppermost stage is closed at the upper end side to form the canopy 4 of the carbon reaction container 1, and the substantially cylindrical body arranged at the lowermost stage is closed at the lower end side to form a carbon reaction container. 1 bottom plate 5 is formed. In addition, an introduction port 6 for taking the source gas into the carbon reaction vessel 1 is formed in the approximate center of the bottom plate 5, and the reaction product gas is made of carbon on the side wall of the substantially cylindrical body located near the canopy 4. An outlet 7 for leading out of the reaction vessel 1 is formed.

  In order to generate a reaction product gas containing trichlorosilane and hydrogen chloride from a raw material gas containing tetrachlorosilane and hydrogen, the carbon reaction vessel 1 is heated from the outside with a heater (not shown) and a carbon reaction vessel is produced. 1 is maintained at 700 to 1400 ° C., the raw material gas supplied from the inlet 6 is reacted inside the carbon reaction vessel 1, and the generated reaction product gas is taken out from the outlet 7.

<Substantially cylindrical body>
As shown in FIG. 3, the substantially cylindrical body 2 has a right cylindrical shape in which male screws are formed on the upper and lower ends involved in the fastening by the ring 3, that is, the outer periphery of the connection upper end portion 8 and the connection lower end portion 9. There are no shoulders or protrusions at the upper end or the lower end like the substantially cylindrical body used in conventional carbon reaction vessels. Therefore, it has an extremely simple shape without large unevenness, and the thickness can be made almost uniform over the entire height direction, so that it has excellent resistance to physical shock and thermal shock.

  The thickness of the substantially cylindrical body 2 is typically preferably 0.5 to 20 cm in order to maintain the strength and to avoid peeling of the silicon carbide coating described later on the surface thereof. More preferably, it is 5 cm to 15 cm.

  Male screws for screwing the substantially cylindrical body 2 to the carbon ring 3 are formed on the outer circumferences of the upper and lower connecting ends 8 and 9 of the substantially cylindrical body 2. The formation width of the male screw is not particularly limited, but is 8/100 or more of the cylindrical height of the substantially cylindrical body 2 in order to ensure the threaded fastening with the ring 3, and further 9 / 100 or more is preferable. The direction of winding of the external thread, the number of threads, the shape of the thread, the diameter and the pitch are not particularly limited.

  The material constituting the substantially cylindrical body 2 is preferably a graphite material having excellent airtightness, and particularly has a high strength due to the fine particle structure, and the characteristics such as thermal expansion are the same in any direction. It is preferable to use isotropic high-purity graphite that is also excellent in heat resistance and corrosion resistance.

<Ring>
As shown in FIG. 4, the ring 3 is a substantially annular ring in which an internal thread is formed on the inner peripheral surface. Similar to the substantially cylindrical body 2, it has an extremely simple shape without large unevenness and has a substantially uniform thickness, and therefore has excellent resistance to physical and thermal shocks.

  The inner diameter of the ring 3 is substantially cylindrical because it is necessary to be screwed to the external threads provided on the outer periphery of the connecting upper end 8 and the connecting lower end 9 of the cylindrical body 2 by a female screw formed on the inner peripheral surface thereof. 2 is almost the same as the outer diameter.

  The radial width (thickness) of the ring 3 is typically 0.5 to 20 cm, preferably 1 in order to maintain strength and to avoid peeling of the silicon carbide coating described later on the surface. It is preferable to set it as 5 cm-15 cm.

  The width (height) of the ring 3 in the direction of the rotation axis is not to be surely screwed to the connection upper end 8 of the one substantially cylindrical body 2 and the connection lower end 9 of the other substantially cylindrical body 2. Don't be. Typically, when the substantially cylindrical body 2 and the ring 3 are screwed together, considering that one of the substantially cylindrical bodies 2 can be screwed only up to half the height of the ring 3, the height of the ring 3 is increased. The height is preferably 10/100 or more and 1/2 or less, more preferably 12/100 or more and 1/2 or less, of the cylindrical height of the cylindrical body 2.

  The winding direction, the number of threads, the shape of the thread groove, the diameter, and the pitch of the female screw formed on the inner peripheral surface of the ring 3 are the outer peripheral surfaces of the connected upper end 8 and the connected lower end 9 of the substantially cylindrical body 2 to be connected. It must correspond to the male screw formed on.

  Moreover, it is preferable that the material which comprises the ring 3 is the same as the material which comprises the substantially cylindrical body 2 so that it may not differ from the substantially cylindrical body 2 extremely in a thermal expansion coefficient.

<Surface treatment>
Since the substantially cylindrical body 2 and the ring 3 are mainly made of carbon, as shown below, the thickness of the tissue is reduced or reduced by hydrogen supplied into the carbon reaction vessel 1 or water generated by hydrogen combustion. It will be embrittled.
C + 2H ₂ → CH ₄
C + H ₂ O → H ₂ + CO
C + 2H ₂ O → 2H ₂ + CO ₂
Since the silicon carbide coating is extremely resistant to such chemical decomposition, it is preferable to form the silicon carbide coating on the surfaces of the substantially cylindrical body 2 and the ring 3 made of carbon.

The silicon carbide film is not particularly limited, but typically can be formed by vapor deposition by a CVD method.
In order to form a silicon carbide coating on the surfaces of the substantially cylindrical body 2 and the ring 3 made of CVD, for example, a silicon halide compound such as tetrachlorosilane or trichlorosilane and a hydrocarbon compound such as methane or propane are used. A method using a mixed gas, or a substantially cylinder heated while thermally decomposing a halogenated silicon compound having a hydrocarbon group such as methyltrichlorosilane, triphenylchlorosilane, methyldichlorosilane, dimethyldichlorosilane, and trimethylchlorosilane with hydrogen. A method of depositing silicon carbide on the surfaces of the body 2 and the ring 3 can be used.

  The thickness of the silicon carbide coating is preferably 10 to 500 μm, more preferably 30 to 300 μm. If the thickness of the silicon carbide coating is 10 μm or more, corrosion of the substantially cylindrical body 2 and the ring 3 caused by hydrogen, water, methane, etc. existing in the carbon reaction vessel 1 can be sufficiently suppressed, and if the thickness is 500 μm or less. Further, cracks in the silicon carbide film and cracks in the structure of the substantially cylindrical body 2 and the ring 3 are not promoted.

  The formed silicon carbide coating is a dense and uniform pinhole-free coating and is excellent in chemical stability. Therefore, the carbon reaction vessel 1 constituted by the substantially cylindrical body 2 and the ring 3 coated with the silicon carbide coating. If the reaction between chlorosilane and hydrogen is carried out, the frequency of repairing the equipment can be reduced, and the work efficiency can be further improved.

<Coefficient of thermal expansion>
In this specification, the “thermal expansion coefficient” means the thickness of the upper connecting end 8 of the substantially cylindrical body 2 at the temperature t ₀ ° C, the thickness of the lower connecting end 9 or the thickness of the ring 3 at a ₀ and the temperature t ₁ ° C. the thickness of the connecting upper end portions 8 of the substantially cylindrical body 2, a thickness or thickness of the ring 3 of the connecting bottom portion 9 in the case of the a _1, obtained by the respective following equations (1).
Thermal expansion coefficient = [(a ₁ −a ₀ ) / a ₀ ] / (t ₁ −t ₀ ) (1)
In order to obtain the coefficient of thermal expansion, it is preferable to measure the amount of thermal expansion under conditions close to the operating conditions of the carbon reaction vessel 1, but the substantially cylindrical body 2 and the ring 3 made of carbon are the same as those of the carbon reaction vessel 1. In any temperature range of 1400 ° C. or less, which is a normal operating condition, the expansion rate with respect to the amount of change in temperature is constant, and thus it is not always necessary to perform measurement by heating to the operating temperature. When used as a carbon reaction vessel for producing a reaction product gas containing trichlorosilane and hydrogen chloride from a raw material gas containing tetrachlorosilane and hydrogen, specifically, t ₀ is set to ₀ to 500 ° C., t _1. It is preferable to measure while raising the ambient temperature at a constant rate using a differential scanning calorimeter under the condition of 400 to 1000 ° C. The measurement is preferably performed in a nitrogen gas atmosphere.

The coefficient of thermal expansion changes depending on the local compositional difference and dimensional error even in the same substantially cylindrical body 2 and ring 3, and may differ depending on the measurement position. In particular, since the substantially cylindrical body 2 and the ring 3 are manufactured by firing carbon, it is difficult to make the composition and dimensions completely uniform.
Accordingly, measurement is performed at a plurality of points on the connection upper end portion 8 of one substantially cylindrical body 2 to obtain an average value thereof, and this average value is set as a thermal expansion coefficient of the connection upper end portion 8 in the approximately cylindrical body 2. preferable. Similarly, it is preferable to obtain an average value for the thermal expansion coefficients of the connecting lower end portion 9 and the ring 3. By using the respective average values as the thermal expansion coefficients of the connection upper end portion 8, the connection lower end portion 9, or the ring 3, it is possible to reduce the influence of such variation in the thermal expansion coefficient depending on the measurement position.

<Assembly of carbon reaction vessel and damage prevention method>
For a plurality of substantially cylindrical bodies 2 for which the thermal expansion coefficients have been obtained in advance, the difference between the thermal expansion coefficient at the connection upper end portion 8 of one of the substantially cylindrical bodies and the thermal expansion coefficient at the connection lower end portion 9 of the other substantially cylindrical body is small. The carbon ring 3 having a smaller difference in thermal expansion coefficient than any of the substantially cylindrical bodies 2 to be connected is used. Fasten the butt end of the substantially cylindrical body.

  Generally, when the substantially cylindrical body 2 and the ring 3 are thermally expanded, their outer diameter and inner diameter increase. As a result, if the expansion amount of the ring 3 exceeds the expansion amount of the substantially cylindrical body 2, a gap may be generated in the connecting portion, resulting in poor airtightness. On the other hand, if the expansion amount of the substantially cylindrical body 2 exceeds the expansion amount of the ring 3 excessively, the stress acting in the radial direction of the connecting portion may increase and cracks may occur. In addition, if the difference in thermal expansion coefficient between the substantially cylindrical bodies 2 connected to each other is large, a gap is formed between the connecting portion and the ring 3, and the source gas and the reaction product gas are outside the carbon reaction vessel. There is a risk of leakage.

  Therefore, the difference in thermal expansion coefficient between the substantially cylindrical bodies 2 connected to each other is arranged in such an order that the difference in thermal expansion coefficient between the cylindrical bodies 2 is reduced. By fastening using the ring 3, it is possible to suppress an increase in stress acting on the connecting portion below an allowable limit, and to improve the airtightness of the connecting portion.

Specifically, in order to sufficiently maintain the airtightness of the connecting portion, the thermal expansion coefficient at the connecting upper end portion 8 of one of the substantially cylindrical bodies connected to each other and the thermal expansion at the connecting lower end portion 9 of the other substantially cylindrical body. The difference from the coefficient is 0.6 × 10 ⁻⁶ (1 / K) or less, more preferably 0.5 × 10 ⁻⁶ (1 / K) or less, more preferably 0.4 × 10 ⁻⁶ (1 / K) or less, more preferably 0.3 × 10 ⁻⁶ (1 / K) or less, more preferably 0.1 × 10 ⁻⁶ (1 / K) or less.

Further, in order to suppress an increase in stress acting on the connecting portion below an allowable limit, the ratio of the thickness of the ring 3 to the thickness of the substantially cylindrical body 2 is 30:70 to 70:30, more preferably 35:65 to 65. : 35, more preferably 40:60 to 60:40, more preferably 45:55 to 55:45, the coefficient of thermal expansion of the ring 3 and the connection upper end 8 and the connection lower end of the substantially cylindrical body 2. The difference from the coefficient of thermal expansion of the portion 9 is 0.4 × 10 ⁻⁶ (1 / K) or less, more preferably 0.3 × 10 ⁻⁶ (1 / K) or less, and further preferably 0.2 × 10 ⁻⁶ (1 / K). Hereinafter, it is more preferable to set it to 0.1 × 10 ⁻⁶ (1 / K) or less.
In particular, it is preferable that the coefficient of thermal expansion at the connection upper end portion 8 and the connection lower end portion 9 of the substantially cylindrical body 2 is smaller than the thermal expansion coefficient of the ring 3 in the connection portion. In this case, it is possible to prevent the substantially cylindrical body 2 from being damaged due to excessive stress applied from the horizontal direction to the connecting upper end 8 and the connecting lower end 9.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these.

A substantially cylindrical body made of isotropic graphite having an outer diameter of 15 cm, a height of 10 cm, and a thickness of 3 cm at 25 ° C. (t ₀ ), the outer peripheral surface and the lower end of the upper end of the connection extending 3.5 cm from the upper end A plurality of substantially cylindrical bodies provided with external threads on the outer peripheral surface of the connecting lower end extending from 3.5 cm to 3.5 cm were prepared. Similarly, the uppermost substantially cylindrical body constituting the canopy of the carbon reaction vessel and the lowermost substantially cylindrical body constituting the bottom plate of the carbon reaction vessel are provided with external threads on the outer peripheral surface of the connection end. . On the other hand, before processing the substantially cylindrical body, a part of the upper end and lower end of the substantially cylindrical body is collected in advance, and the thermal expansion coefficient corresponding to the connected upper end portion and the connected lower end portion of the substantially cylindrical body from the portion. A test piece for measuring was cut out. Four test pieces were prepared for each of the upper end and the lower end in a size of 5 mm in length, 5 mm in width, and 15 mm in height.

  Next, in order to form a silicon carbide coating on the inner and outer peripheral surfaces of these approximately cylindrical bodies, the approximately cylindrical body is placed in a CVD reactor, and the interior of the apparatus is replaced with argon gas, and then heated to 1200 ° C. did. A mixed gas of trichloromethylsilane and hydrogen (molar ratio 1: 5) was introduced into the CVD reactor, and a silicon carbide film having a thickness of 200 μm was formed on the entire surface of the substantially cylindrical body by the CVD method.

Next, a ring made of isotropic graphite having an inner diameter of 15 cm, an up-and-down width of 7.5 cm, and a radial thickness of 3.6 cm at 25 ° C. (t ₀ ) is formed on the inner peripheral surface of the substantially cylindrical body. A plurality of rings formed with female threads to be engaged with the formed male threads were prepared, and a silicon carbide coating was applied to the entire surface in the same manner as described above. Before processing the ring, a part of the upper end or the lower end of the ring was collected in advance, and a test piece for measuring the thermal expansion coefficient corresponding to the ring was cut out from the portion. The test piece was prepared in a size of 5 mm in length, 5 mm in width, and 15 mm in height, 4 points at a time.

About the test piece corresponding to the connection upper end part and connection lower end part of each substantially cylindrical body, the atmospheric temperature is constant from 25 ° C. (t ₀ ) to 1100 ° C. (t ₁ ) using a differential scanning calorimeter in a nitrogen gas atmosphere. The coefficient of thermal expansion was determined while increasing at a speed, and these were used as the coefficient of thermal expansion of the upper and lower ends of each substantially cylindrical body. Similarly, the coefficient of thermal expansion was determined for the test piece collected from each ring, and this was used as the coefficient of thermal expansion of each ring.

  The difference between the average thermal expansion coefficient of the connection upper end portion of one of the substantially cylindrical bodies and the average thermal expansion coefficient of the connection lower end portion of the other substantially cylindrical body, and the connection portion. The cylindrical body is fastened with a ring so that the difference between the average thermal expansion coefficient of the upper end of the connection of the substantially cylindrical body located on the lower side and the average thermal expansion coefficient of the ring is within a certain range shown in Tables 1 and 2. A carbon reaction vessel was produced.

Piping and a heating device were set in the produced carbon reaction vessel to prepare a reaction furnace.
A mixed gas of tetrachlorosilane and hydrogen (mole = 1: 1) was supplied to the reactor, and the reaction was performed at normal pressure and a reaction temperature of 1100 ° C. to produce trichlorosilane.
After the reactor was continuously operated for 2000 hours, the amount of the raw material gas and the reaction product gas leaked from the carbon reactor into the reactor was measured to evaluate the airtightness, and then the carbon reactor was disassembled. The occurrence of cracks in the connecting part of the substantially cylindrical body was observed. The results are shown in Tables 1 and 2.

^＊１略円筒体間の熱膨張係数差＝［連結部において上側に位置する略円筒体の連結下端部の熱膨張係数］−［連結部において下側に位置する略円筒体の連結上端部の熱膨張係数］
^＊２リングとの熱膨張係数差＝［リングの熱膨張係数］−［連結部において下側に位置する略円筒体の連結上端部の熱膨張係数］

^{* 1} Difference in thermal expansion coefficient between substantially cylindrical bodies = [thermal expansion coefficient of a connecting lower end portion of a substantially cylindrical body located on the upper side in the connecting portion]-[of connecting upper end portion of a substantially cylindrical body located on the lower side in the connecting portion. Thermal expansion coefficient]
^{* 2} Difference in thermal expansion coefficient from the ring = [thermal expansion coefficient of the ring] − [thermal expansion coefficient of the connection upper end portion of the substantially cylindrical body located on the lower side in the connection portion]

<Experimental considerations>
From the above results, the difference between the thermal expansion coefficient at the connection upper end of one of the substantially cylindrical bodies and the thermal expansion coefficient at the connection lower end of the other substantially cylindrical body is 0.1 × 10 ⁻⁶ (1 / K). It was confirmed that the airtightness was improved by the following.

In addition, the thermal expansion coefficient of the connection upper end portion and the connection lower end portion of the substantially cylindrical body in the connection portion is made smaller than the thermal expansion coefficient of the ring, and the thermal expansion coefficient of the ring and the connection upper end portion and connection lower end portion of the substantially cylindrical body. It was confirmed that when the difference from the coefficient of thermal expansion is 0.3 × 10 ⁻⁶ (1 / K) or less, an increase in stress acting on the connecting portion can be suppressed to an allowable limit or less and airtightness can be maintained.

  In the above, this invention was demonstrated based on the Example. It is to be understood by those skilled in the art that this embodiment is merely an example, and that various modifications are possible and that such modifications are within the scope of the present invention.

Claims (5)

  A plurality of substantially cylindrical bodies made of carbon are arranged in such an order that the difference between the thermal expansion coefficient at the upper end of the connection of one of the substantially cylindrical bodies and the thermal expansion coefficient at the lower end of the connection of the other substantially cylindrical body is reduced. A method for preventing damage to a carbon reaction vessel, wherein the ends are butted substantially coaxially, and the butted ends are fastened with a carbon ring having a small difference from the thermal expansion coefficient of the substantially cylindrical body.   The method for preventing damage to a carbon reaction vessel according to claim 1, wherein the substantially cylindrical body is made of graphite.   The method for preventing damage to a carbon reaction vessel according to claim 1, wherein the inner peripheral surface and / or the outer peripheral surface of the substantially cylindrical body is treated with a silicon carbide coating. The difference between the coefficient of thermal expansion at the connection upper end of one of the substantially cylindrical bodies connected to each other and the coefficient of thermal expansion at the connection lower end of the other substantially cylindrical body is 0.1 × 10 ⁻⁶ (1 / K) or less. Item 2. A method for preventing damage to a carbon reaction vessel according to Item 1. Ring thickness: When the thickness of the substantially cylindrical body is in the range of 30:70 to 70:30, the thermal expansion coefficients of the connection upper end and the connection lower end of the cylinder are smaller than the thermal expansion coefficient of the ring. The carbon reaction according to claim 1, wherein the difference between the thermal expansion coefficient of the ring and the thermal expansion coefficients of the upper and lower ends of the substantially cylindrical body is 0.3 × 10 ⁻⁶ (1 / K) or less. Container breakage prevention method.

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