JPWO2010113322A1 - How to prevent damage to carbon reaction vessels - Google Patents

Abstract

The present invention relates to a method for preventing breakage of a reaction vessel made of carbon, which can prevent the occurrence of cracking of a connecting portion due to thermal expansion, and has a protruding portion with an outer diameter reduced at one end and the other A plurality of carbon-made substantially cylindrical bodies having shoulders whose inner diameters are enlarged at the end portions, and a coefficient of thermal expansion at the projecting portion of one of the substantially cylindrical bodies and a coefficient of thermal expansion at the shoulder of the other substantially cylindrical body. They are connected in such an order that the difference becomes smaller.

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, even if they are substantially cylindrical bodies that seem to be identically manufactured using the same material and have the same shape and dimensions, It was found that the thermal expansion coefficient is different for each cylinder. Therefore, by measuring the thermal expansion coefficient of each substantially cylindrical body in advance, and connecting the substantially cylindrical bodies in such an order that the difference in thermal expansion coefficient between the shoulder portion to be connected and the protruding portion is reduced, a carbon reaction is achieved. The inventors have found that the container can be prevented from being damaged by thermal shock, and have reached the present invention.

  That is, the method for preventing breakage of the carbon reaction container according to the present invention includes a protrusion having a reduced outer diameter at one end and a shoulder having an increased inner diameter at the other end. The plurality of substantially cylindrical bodies are connected in such an order that the difference between the thermal expansion coefficient at the projecting portion of one substantially cylindrical body and the thermal expansion coefficient at the shoulder of the other substantially cylindrical body is reduced. .

  By adopting such a configuration, in each connecting portion, it is possible to reduce the difference between the thermal expansion amount of the protruding portion of one substantially cylindrical body and the thermal expansion amount of the shoulder portion of the other substantially cylindrical body, It is possible to suppress an increase in stress applied to the weak shoulder portion and the protruding portion, and to prevent the carbon reaction vessel from being damaged.

It is a schematic longitudinal cross-sectional view which shows one form of the carbon-made reaction containers handled in this invention. It is an enlarged view of the connection part between the substantially cylindrical bodies enclosed with the round frame A of FIG.

100: carbon reaction vessel 101: substantially cylindrical body 102: shoulder 103: protrusion 104: body 105: canopy 106: bottom plate 107: inlet 108: outlet 109: shoulder thickness 110: protrusion thickness 111 : Body thickness 112: R 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. 1, the carbon reaction vessel 100 handled in the present embodiment includes a plurality of substantially cylindrical bodies made of carbon such that the lower end of one substantially cylindrical body 101 is fitted to the upper end of the other substantially cylindrical body 101. It is comprised by arrange | positioning 101 and arrange | positioning up and down substantially coaxially.
The substantially cylindrical body arranged at the uppermost stage is closed at the upper end side to constitute the canopy 105 of the carbon reaction vessel 100, and the substantially cylindrical body arranged at the lowermost stage is closed at the lower end side to form a carbon reaction vessel. 100 bottom plates 106 are formed. In addition, an introduction port 107 for taking the raw material gas into the carbon reaction vessel 100 is formed in the approximate center of the bottom plate 106, and the reaction product gas is made of carbon on the side wall of the substantially cylindrical body located in the vicinity of the canopy 105. An outlet 108 for leading the reaction vessel 100 to the outside is formed.

  In order to generate a reaction product gas containing trichlorosilane and hydrogen chloride from a raw material gas containing tetrachlorosilane and hydrogen, this carbon reaction vessel 100 is heated from the outside with a heater (not shown) and a carbon reaction vessel is produced. The internal temperature of 100 is kept at 700 to 1400 ° C., the raw material gas supplied from the inlet 107 is reacted inside the carbon reaction vessel 100, and the generated reaction product gas is taken out from the outlet 108.

<Substantially cylindrical body>
As shown in FIG. 1, the substantially cylindrical body 101 has a protruding portion 103 in which the outer diameter of one end portion is reduced, and a shoulder portion 102 in which the inner diameter of the other end portion is enlarged.
In the carbon reaction vessel 100 used in the present embodiment, the inner diameter of the upper end of the substantially cylindrical body 101 is larger than the inner diameter of the body part 104, and the shoulder part 102 is formed by a step caused by the inner diameter difference between the upper end and the body part 104. Is formed. In addition, the outer diameter of the lower end of the substantially cylindrical body 101 is reduced from the outer diameter of the body portion 104, and the protruding portion 103 is formed by a step caused by the outer diameter difference between the lower end and the body portion 104.

  As shown in FIG. 2 in an enlarged manner, the ratio of the thickness 109 of the shoulder portion to the thickness 110 of the protruding portion with respect to the radial direction of the substantially cylindrical body 101 is 30:70 to 70:30, more preferably 35:65 to 65: 35, more preferably in the range of 40:60 to 60:40, and more preferably about 45:55. By setting the thicknesses of the shoulder portion 102 and the protruding portion 103 in such a range, the difference in the thermal expansion coefficient between the substantially cylindrical bodies 101 to be connected is set to a specific value or less, which will be described later, so that the shoulder portion 102 and the protruding portion 103 are. As a result, it is possible to prevent excessive stress from being applied, and at the same time to maintain airtightness at the connecting portion.

  The thickness 111 of the body portion of the substantially cylindrical body 101 is typically 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. Preferably, it is 1.5 cm to 15 cm.

  In addition, a curved recess (R portion 112) is provided at the base of the shoulder portion 102 and the protruding portion 103. The radius of curvature of the R portion 112 is preferably 5 to 10% of the thickness 111 of the body portion, and more preferably 5 to 7%. By providing the R portion 112, it is possible to disperse the stress applied to the base of the shoulder portion 102 and the protruding portion 103, which are likely to start cracks, and to further prevent the carbon reaction vessel 100 from being damaged. Further, if the radius of curvature of the R portion 112 is within this range, the thickness of the substantially cylindrical body 101 does not become excessively thin, so that the strength can be sufficiently maintained.

  Screws for screwing and fastening a plurality of substantially cylindrical bodies 101 are formed on the inner peripheral surface of the shoulder portion 102 and the outer peripheral surface of the protruding portion 103. By screwing and fastening the substantially cylindrical bodies 101 to each other, it is possible to improve the connection stability and at the same time to obtain sufficient airtightness. The direction of winding of the screw to be formed, the number of threads, the shape of the thread, the diameter, and the pitch are not particularly limited. It is not always necessary to screw and fasten the plurality of substantially cylindrical bodies 101, and an appropriate sealing material such as a cement material may be applied to the connecting portion to ensure stability and airtightness.

  Further, as the material constituting the substantially cylindrical body 101, a graphite material having excellent airtightness is preferable. In particular, because of the fine particle structure, the strength is high, 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.

<Surface treatment>
Since the substantially cylindrical body 101 is mainly made of carbon, as shown below, the thinning or embrittlement of the tissue is caused by hydrogen supplied into the carbon reaction vessel 100 or water generated by hydrogen combustion. I will receive it.
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 surface of the substantially cylindrical body 101 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 film on the surface of the substantially cylindrical body 101 made of carbon by the CVD method, for example, a mixed gas of a silicon halide compound such as tetrachlorosilane or trichlorosilane and a hydrocarbon compound such as methane or propane is used. The method of using, or heating the substantially cylindrical body 101 while pyrolyzing a silicon halide compound having a hydrocarbon group such as methyltrichlorosilane, triphenylchlorosilane, methyldichlorosilane, dimethyldichlorosilane, and trimethylchlorosilane with hydrogen. A method of depositing silicon carbide on the surface 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 101 caused by hydrogen, water, methane, etc. existing in the carbon reaction vessel 100 can be sufficiently suppressed, and if it is 500 μm or less, silicon carbide Neither cracking of the coating nor cracking of the structure of the substantially cylindrical body 101 is promoted.

  The formed silicon carbide coating is a dense and uniform pinhole-free coating and is excellent in chemical stability. Therefore, chlorosilane is contained in the carbon reaction vessel 100 constituted by the substantially cylindrical body 101 provided with the silicon carbide coating. If hydrogen is reacted with hydrogen, the frequency of repairing the equipment can be reduced and the work efficiency can be further improved.

<Coefficient of thermal expansion>
As used herein, "thermal expansion coefficient", a shoulder thickness 109 or protrusion of the thickness 110 of the temperature t ₀ ° C. a _0, a thickness 109 or protrusion of the thickness 110 of the shoulder at a temperature t ₁ ° C. when 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 thermal expansion coefficient, it is preferable to measure the amount of thermal expansion under conditions close to the operating conditions of the carbon reaction vessel 100, but the substantially cylindrical body 101 made of carbon is the normal operating condition of the carbon reaction vessel 100. In any temperature range of 1400 ° C. or lower, the expansion rate with respect to the amount of change in temperature is constant. 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 varies depending on the position to be measured because it changes due to local compositional differences and dimensional errors even in the same substantially cylindrical body 101. In particular, since the substantially cylindrical body 101 is manufactured by firing carbon, it is difficult to make the composition and dimensions completely uniform.
Therefore, it is preferable to measure the shoulder portion 102 of one substantially cylindrical body 101 at a plurality of points, obtain an average value thereof, and use this average value as the thermal expansion coefficient of the shoulder portion 102 in the substantially cylindrical body 101. Similarly, it is preferable to obtain an average value for the thermal expansion coefficient of the protrusion 103. By using the respective average values as the thermal expansion coefficients of the shoulder portion 102 and the protruding portion 103, 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 101 whose thermal expansion coefficients have been obtained in advance, the difference between the thermal expansion coefficient in the shoulder 102 of one substantially cylindrical body and the thermal expansion coefficient in the protruding part 103 of the other substantially cylindrical body is reduced. And the projecting portion 103 of the other substantially cylindrical body is sequentially screwed into the shoulder portion 102 of the one substantially cylindrical body and fastened.

  Generally, when the substantially cylindrical body 101 is thermally expanded, its outer diameter and inner diameter increase. As a result, if the expansion amount of the shoulder portion 102 is excessively larger than the expansion amount of the protruding portion 103, a gap may be generated in the connecting portion, resulting in poor airtightness. On the other hand, if the expansion amount of the protruding portion 103 exceeds the expansion amount of the shoulder portion 102 excessively, the stress acting in the radial direction at the connecting portion may increase and cracks may occur.

Thus, by connecting in such an order that the difference in coefficient of thermal expansion between the substantially cylindrical bodies 101 that are connected to each other is reduced in this way, an increase in stress acting on the connecting portion can be suppressed to an allowable limit or less. At the same time, the airtightness of the connecting portion can be improved.
Specifically, when the thickness 109 of the shoulder portion and the thickness 110 of the projecting portion are in the range of 30:70 to 70:30, the thermal expansion coefficients of the shoulder portion 102 and the projecting portion 103 of the substantially cylindrical body 101 to be connected. The difference is 0.4 × 10 ⁻⁶ (1 / K) or less, more preferably 0.3 × 10 ⁻⁶ (1 / K) or less, more preferably 0.2 × 10 ⁻⁶ (1 / K) or less, and further preferably 0.1 × 10 10. ^-6 (1 / K) or less is preferable.
In particular, the thermal expansion coefficient of the protrusion 103 of one substantially cylindrical body (substantially cylindrical body located on the upper side) in the connecting portion is the same as that of the shoulder 102 of the other substantially cylindrical body (substantially cylindrical body located on the lower side). By combining the substantially cylindrical body 101 so as to be larger than the thermal expansion coefficient, it is possible to manufacture a carbon reaction vessel that is less likely to crack and has excellent airtightness.

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.
For example, in the carbon reaction vessel 100 used in the present embodiment, the case where the shoulder portion 102 is provided at the upper end of the substantially cylindrical body 101 and the protruding portion 103 is provided at the lower end has been described, but the protruding portion 103 is provided at the upper end. It may be provided and a shoulder 102 may be provided at the lower end.

  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 ), having a depth of 3.8 cm at the upper end and a thickness in the radial direction. A plurality of substantially cylindrical bodies having a 1.35 cm shoulder and a protruding portion having a length of 3.8 cm and a radial thickness of 1.65 cm at the lower end were prepared. A screw groove was formed on the inner peripheral surface of the shoulder, and a screw thread corresponding to the screw groove was formed on the outer peripheral surface of the protrusion. In addition, before processing the substantially cylindrical body, a part of the upper end and the lower end of the substantially cylindrical body is collected in advance, and the thermal expansion coefficient corresponding to the shoulder portion and the protruding portion of the substantially cylindrical body is measured from the portion. A test piece 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.

On the other hand, certain individual for substantially cylindrical body shoulder and the corresponding specimen protrusions, in a nitrogen gas atmosphere, to 25 ° C. The ambient temperature using a differential scanning calorimeter _{(t 0) ~1100 ℃ (t} 1) The coefficient of thermal expansion was determined while increasing at a speed, and these were used as the coefficient of thermal expansion of the shoulder and protrusion of each substantially cylindrical body.

  The substantially cylindrical body is connected so that the difference between the thermal expansion coefficient of the shoulder portion of one substantially cylindrical body to be connected and the thermal expansion coefficient of the projecting portion of the other substantially cylindrical body is within a certain range shown in Table 1, 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 Table 1.

^＊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突出部の熱膨張係数］−［連結部において下側に位置する略円筒体の肩部の熱膨張係数］

^{* 1} Difference in thermal expansion coefficient between substantially cylindrical bodies = [thermal expansion coefficient of a protruding portion of a substantially cylindrical body located on the upper side in the connecting portion] − [thermal expansion of a shoulder portion of a substantially cylindrical body located on the lower side in the connecting portion coefficient]

<Experimental considerations>
From the above results, it was confirmed that if the difference in thermal expansion coefficient between the substantially cylindrical bodies connected to each other is 0.1 × 10 ⁻⁶ or less, the connecting portion is not cracked and damage to the carbon reaction vessel can be prevented. . In particular, when the thermal expansion coefficient at the projecting portion of one substantially cylindrical body to be connected is larger than the thermal expansion coefficient at the shoulder portion of the other substantially cylindrical body, and the difference between the two is 0.1 × 10 ⁻⁶ or less. It was confirmed that particularly excellent effects can be obtained in terms of both crack generation and airtightness.

  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 (7)

  A plurality of substantially cylindrical bodies made of carbon having a projecting portion whose outer diameter is reduced at one end and a shoulder portion whose inner diameter is enlarged at the other end are projected from one of the substantially cylindrical bodies. The carbon reaction vessel is prevented from being damaged by connecting in such an order that the difference between the coefficient of thermal expansion in the section and the coefficient of thermal expansion in the shoulder of the other substantially cylindrical body is reduced.   The method for preventing damage to a carbon reaction vessel according to claim 1, wherein the thickness of the shoulder with respect to the radial direction of the substantially cylindrical body: the thickness of the protrusion is in the range of 30:70 to 70:30.   The method for preventing damage to a carbon reaction vessel according to claim 1, wherein a curved recess (R portion) is provided at the base of the shoulder portion and the protruding portion.   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. Shoulder thickness: When the thickness of the protrusion is in the range of 30:70 to 70:30, the difference in thermal expansion coefficient between the shoulder and the protrusion is 0.1 × 10 ⁻⁶ (1 / K) or less. The method for preventing damage to a carbon reaction vessel according to claim 1, wherein the substantially cylindrical bodies are connected to each other. Shoulder thickness: When the thickness of the protrusion is in the range of 30:70 to 70:30, the thermal expansion coefficient of the protrusions connected to each other is greater than the thermal expansion coefficient of the shoulder, and the difference is 0 The method for preventing damage to a carbon reaction vessel according to claim 1, wherein the substantially cylindrical bodies are connected to each other so as to be 1 × 10 ⁻⁶ (1 / K) or less.

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