JP4463050B2 - Carbon fiber firing furnace - Google Patents

Description

  The present invention relates to a carbon fiber firing furnace for carbonizing a flame resistant fiber when producing carbon fiber.

  In a method for producing pitch-based or polyacrylonitrile (PAN) -based carbon fibers, usually, the fibers are first subjected to flame resistance treatment using a heat treatment apparatus having an internal temperature of 300 ° C. or lower to obtain flame-resistant fibers.

  Next, the flame-resistant fiber is guided to a baking furnace at 400 ° C. or higher in an inert gas atmosphere, and after first carbonized at 400 to 800 ° C. as necessary, second carbonized at 1000 ° C. or higher. Carbonization is performed by firing.

  In the carbon fiber firing furnace, a large amount of gas (generated gas) is generated with carbonization, and 10 to 40% by mass of the flame resistant fiber strand supplied to the carbon fiber firing furnace is gasified. This gas passes through the exhaust port together with the inert gas and is discharged out of the firing furnace (see, for example, Patent Document 1).

  FIG. 6 is a schematic view showing an example of a conventional firing furnace, (I) shows the movement of gas generated during the firing furnace operation (state of generated gas flow) and the movement of inert gas, (II) Shows a state in which foreign matter such as powder, kerva and tar adheres to the inner wall and ceiling portion on the strand inlet side and outlet side of the firing furnace and the vicinity thereof, and a state in which these foreign matters fall off on the strand.

  As shown in FIG. 6, in the conventional carbon fiber firing furnace 32, when carbonizing the strand 34 that travels in the carbon fiber firing furnace 32 a by forming a path 34 a horizontally, the generated gas 52 is generated in the carbon fiber firing furnace 32. It spreads along the ceiling 44. This generated gas 52 is normally discharged out of the system from an exhaust port 40 provided in the ceiling 44 of the carbon fiber firing furnace 32.

  The generated gas 52 that spreads along the ceiling 44 of the carbon fiber firing furnace 32 has a relatively low temperature and a gas flow hardly occurs (so-called dead space), ie, the ceiling 62 on the strand entrance side and the inner wall on the strand entrance side. It stays in the vicinity of 64 as a staying gas 52a for a long time. Alternatively, the gas stays in the vicinity of the ceiling 66 on the strand outlet side and the inner wall 68 on the strand outlet side as a staying gas 52c for a long time.

  While part of the generated gas 52 stays as the staying gas 52a or staying gas 52c, the strand 62 side ceiling 62 or the strand entrance side inner wall 64, or the strand exit side ceiling 66 or the strand exit side A part of the inner wall 68 touches and adheres to the wall surface as a liquid foreign substance such as condensed tar.

  In the case where the strand is oil-treated with a sizing agent such as silicone oil, silica powder and erosion generated by thermal decomposition are generated. A part of these powders and marks adheres to the surface of the liquid foreign matter and accumulates on the inner wall and ceiling on the strand inlet side and outlet side as solid-liquid mixed foreign matter 62a, 64a, 66a, 68a.

These accumulated solid-liquid mixed foreign matter becomes a high density as the amount of deposition increases, falls on the strands, and becomes solid-liquid mixed foreign matter 72 and 74 that contaminate the strands. These solid-liquid mixed foreign substances 72 and 74 not only deteriorate the quality of the strand but also cause the strand to be cut.
JP-A-62-85029 (pages 2 to 4)

  As a result of earnestly examining the above problems, the present inventor has specified a strand introduction portion of a carbon fiber firing furnace in a carbon fiber firing furnace that produces carbon fiber by carbonizing a flameproof fiber running in the carbon fiber firing furnace. It has been found that the shape can prevent contamination, cutting, and deterioration of the flame-resistant fiber and carbon fiber due to the drop of foreign matter, and the present invention has been completed.

  Accordingly, an object of the present invention is to provide a carbon fiber firing furnace that solves the above-mentioned problems.

  The present invention for achieving the above object is described below.

[1] In a carbon fiber firing furnace for carbonizing a flame-resistant fiber strand running in a carbon fiber firing furnace horizontally and parallel to the length direction of the carbon fiber firing furnace in an inert gas atmosphere, the carbon fiber firing A strand introduction part in which the furnace is (A) a length of 1/50 or more of the length of the carbon fiber firing furnace from the strand inlet end of the carbon fiber firing furnace and the ceiling height gradually increases in the strand running direction;
(B) The main body part formed continuously from the strand introduction part (A) and having a ceiling height in the direction of running of the strand and (C) the exhaust provided on the ceiling of the carbonization main part (B) And a carbon fiber firing furnace having a port.

[2] In a carbon fiber firing furnace that carbonizes a flame-resistant fiber strand that travels horizontally in the carbon fiber firing furnace and parallel to the length direction of the carbon fiber firing furnace in an inert gas atmosphere. A strand introduction part in which the furnace is (A) a length of 1/50 or more of the length of the carbon fiber firing furnace from the strand inlet end of the carbon fiber firing furnace and the ceiling height gradually increases in the strand running direction;
(B) The main body portion formed following the strand introduction portion (A), the ceiling height of which is constant toward the strand running direction,
(C) An exhaust port provided on the ceiling of the carbonized main part (B) and (D) a carbon fiber fired formed following the main part (B) and formed from the main part rear end to the strand outlet end. A carbon fiber firing furnace having a strand take-out portion that has a length of 1/50 or more of the entire length of the furnace and whose ceiling height gradually decreases in the strand running direction.

  [3] The carbon fiber firing furnace according to [1] or [2], wherein an inert gas introduction portion (E) is provided below the strand introduction portion (A).

  [4] The carbon fiber firing furnace according to [1] or [2], wherein the exhaust port (C) is provided on the ceiling of the end portion on the strand outlet side of the carbonization main portion (B).

  [5] The carbon fiber firing furnace according to [1] or [2], wherein the gradual increase in the ceiling height of the strand introduction portion (A) is linear.

  [6] The carbon fiber firing furnace according to [2], wherein the gradual decrease in the ceiling height of the strand take-out portion (D) is linear.

  When the carbon fiber firing furnace of the present invention is used to carbonize a flame-resistant fiber strand that travels in the carbon fiber firing furnace, particularly an oil-treated strand, the carbon fiber firing furnace of the present invention is disposed at the strand inlet end. Since the strand introduction portion (A) whose ceiling height gradually increases in the strand running direction is provided, there are few portions where the gas flow generated in the carbon fiber firing furnace stays for a long time. If a strand take-out portion (D) in which the ceiling height gradually decreases in the strand running direction at the strand exit end, the portion where the gas flow generated in the carbon fiber firing furnace stays for a long time is further reduced.

  As a result, almost no solid-liquid mixed foreign matter adheres to the ceiling or inner wall of the carbon fiber firing furnace, so that the solid-liquid mixed foreign matter can be prevented from falling onto the running strand, and the flame-resistant fiber strand and carbonized strand are contaminated and cut. Deterioration can be prevented. Therefore, stable carbonization of the strand can be performed.

  Hereinafter, the present invention will be described in detail with reference to FIG.

  FIG. 1 is a schematic view showing an example of a carbon fiber firing furnace of the present invention. In FIG. 1, 2 is a carbon fiber firing furnace, and the inside is an elongated hollow firing chamber 2a. In the firing chamber 2a, the strand 4 is fired while traveling along the strand path 4a in parallel and horizontally with the length direction of the carbon fiber firing furnace 2.

  Reference numeral 6 denotes a strand introduction port formed at one end of the carbon fiber firing furnace 2, and the strand 4 introduced into the firing chamber 2a from the strand introduction port 6 travels in the firing chamber 2a in parallel and horizontally in the length direction. While being heated and fired, it is taken out from the strand outlet 8 formed at the other end of the carbon fiber firing furnace 2.

  The ceiling in the firing chamber 2 a is formed with a strand introduction portion A that gradually increases from the strand inlet 6 toward the strand outlet 8. The strand introduction portion A needs to be 1/50 or more of the length in the length direction (full length) of the carbon fiber firing furnace 2, and more preferably 1/20 to 1/10.

  Following the strand introduction portion A, a carbonization main portion B having the same height of the ceiling 14 is formed in the direction of the strand outlet 8. Reference numeral 10 denotes an exhaust port formed on the ceiling of the carbonization main portion B.

  Next, a case where the flame resistant fiber is carbonized using the carbon fiber firing furnace will be described.

  In FIG. 1, the strand 4 introduced from the strand introduction port 6 is first preheated at the strand introduction portion A and is heat-treated until it passes through the firing chamber 2 a and is taken out from the strand outlet 8.

  The gas 22 generated at this time moves in the direction of the strand outlet 8 along the path 26 of the generated gas without staying in the space where the strand introduction portion A is narrow, and is discharged from the exhaust port 10 to the outside. Is done.

  The strand (flame-resistant fiber strand) supplied to the carbon fiber firing furnace forms a strand path 4a horizontally and parallel to the side wall of the carbon fiber firing furnace 2 in the firing chamber 2a heated to 400 ° C. or higher. And is heated (carbonized) to become carbon fiber. This carbon fiber firing furnace 2 is carbonized (first carbonization treatment) in the first stage carbonization furnace heated to 400 to 800 ° C. as it goes from the inlet side to the outlet side of the path 4a as necessary. Further, it may be composed of a two-stage carbonization furnace that performs carbonization (second carbonization treatment) in a second-stage carbonization furnace at a later stage. In the case of a two-stage carbonization furnace, the carbon fiber firing furnace 2 is preferably used as the first stage carbonization furnace.

  It is preferable that the ceiling 12 of the strand introduction part (A) increases linearly in the strand running direction. As a result, the stay of the generated gas in the carbon fiber firing furnace is particularly reduced, and the solid-liquid mixed foreign matter is particularly less deposited on the ceiling and wall surface in the carbon fiber firing furnace.

  As described above, in the carbon fiber firing furnace 2 of the present invention, the generated gas 22 in the firing chamber 2a is discharged outside the system toward the exhaust port 10 without causing partial retention for a long period of time. Therefore, the generation of solid-liquid mixed foreign matters due to the generated gas 22 is reduced, and strand contamination, cutting, and deterioration can be prevented.

  Further, as shown in FIG. 3, the carbon fiber firing furnace 2 can be provided with an inert gas inlet 18, from which the inert gas supplied into the carbon fiber firing furnace passes through a path exemplified by 24. The gas is discharged from the exhaust port 10 to the outside. The effect of supplying an inert gas (for example, nitrogen gas) is effective not only for preventing the oxidation of the strands but also forcibly discharging the generated gas from the strands. Other reference numerals in FIG. 3 are the same as those in FIG.

  FIG. 2 is a schematic view showing another example of the carbon fiber firing furnace of the present invention. In FIG. 2, 2 is a carbon fiber firing furnace, and the inside is an elongated hollow firing chamber 2a. In the firing chamber 2a, the strand 4 is fired while traveling along the strand path 4a in parallel and horizontally with the length direction of the carbon fiber firing furnace 2.

  Reference numeral 6 denotes a strand introduction port formed at one end of the carbon fiber firing furnace 2, and the strand 4 introduced into the firing chamber 2a from the strand introduction port 6 travels in the firing chamber 2a in parallel and horizontally in the length direction. While being heated and fired, it is taken out from the strand outlet 8 formed at the other end of the carbon fiber firing furnace 2.

  The ceiling in the firing chamber 2 a is formed with a strand introduction portion A that gradually increases from the strand inlet 6 toward the strand outlet 8. The strand introduction portion A needs to be 1/50 or more of the length in the length direction (full length) of the carbon fiber firing furnace 2, and more preferably 1/20 to 1/10.

  Following the strand introduction portion A, a carbonization main portion B having the same height of the ceiling 14 is formed in the direction of the strand outlet 8.

  Following the carbonization main part B, a strand take-out part D is formed which gradually decreases as the height of the ceiling 16 moves toward the strand take-out port 8. The strand take-out portion D needs to be 1/50 or more of the length in the length direction (full length) of the carbon fiber firing furnace 2, and more preferably 1/20 to 1/10.

  Reference numeral 18 denotes an inert gas inlet formed in the vicinity of the strand inlet 6, from which an inert gas is introduced into the carbon fiber firing furnace 2. Reference numeral 10 denotes an exhaust port formed on the ceiling of the carbonization main portion B.

  Next, a case where the flame resistant fiber is carbonized using the carbon fiber firing furnace will be described.

  In FIG. 2, the strand 4 introduced from the strand introduction port 6 is first preheated at the strand introduction portion A, and is carbonized before passing through the firing chamber 2 a and being taken out from the strand outlet 8.

  The gas 22 generated at this time does not stay in this portion because the space of the strand introduction portion A is narrow, and is carried along with the inert gas introduced from 18 and moves in the direction of the strand outlet 8. The gas moves in the direction of the strand outlet 8 along the gas path 26 and is discharged to the outside from the exhaust port 10. Further, the generated gas 22 is discharged outside from the exhaust port 10 without staying in this portion because the space of the strand extraction portion D is narrow.

  The strand (flame-resistant fiber strand) supplied to the carbon fiber firing furnace forms a strand path 4a horizontally and parallel to the side wall of the carbon fiber firing furnace 2 in the firing chamber 2a heated to 400 ° C. or higher. And is heated (carbonized) to become carbon fiber. This carbon fiber firing furnace 2 is carbonized (first carbonization treatment) in the first stage carbonization furnace heated to 400 to 800 ° C. as it goes from the inlet side to the outlet side of the path 4a as necessary. Further, it may be composed of a two-stage carbonization furnace that performs carbonization (second carbonization treatment) in a second-stage carbonization furnace at a later stage. In the case of a two-stage carbonization furnace, the carbon fiber firing furnace 2 is preferably used as the first stage carbonization furnace.

  The ceiling 12 of the strand introduction part (A) increases linearly in the strand running direction, and the ceiling 16 of the strand take-out part (D) decreases linearly in the strand running direction. Preferably it is. As a result, the stay of the generated gas in the carbon fiber firing furnace is particularly reduced, and the solid-liquid mixed foreign matter is particularly less deposited on the ceiling and wall surface in the carbon fiber firing furnace.

  Further, the carbon fiber firing furnace 2 is provided with an inert gas inlet 18, from which the inert gas supplied into the carbon fiber firing furnace passes through an exhaust port 10 through the path exemplified by 24. Discharged. The effect of supplying an inert gas (for example, nitrogen gas) is effective not only for preventing the oxidation of the strands but also forcibly discharging the generated gas from the strands.

  As described above, in the carbon fiber firing furnace 2 of the present invention, the generated gas 22 in the firing chamber 2a is discharged outside the system toward the exhaust port 10 without causing partial retention for a long period of time. Therefore, the generation of solid-liquid mixed foreign matters due to the generated gas 22 is reduced, and strand contamination, cutting, and deterioration can be prevented.

  Hereinafter, although the carbon fiber baking furnace of this invention is demonstrated using an Example and a comparative example, this invention is not limited to these Examples and a comparative example.

Example 1
In the carbon fiber firing furnace shown in FIG. 4, the carbon fiber is carbonized by supplying an acrylic fiber-based strand 4 subjected to oil treatment (addition of 2% by mass of silicone oil as a sizing agent to the strand) at a supply rate of 1.5 kg / min. It was.

  The specifications of the carbon fiber firing furnace are as follows: the total length of the carbon fiber firing furnace (Lt) 12 m, the total height of the carbon fiber firing furnace (Ht) 0.4 m, the total width of the carbon fiber firing furnace (Wt) 1.6 m, Length (La) 1 m, length of carbonization main part (Lb) 11 m, length from exhaust port end to carbon fiber firing furnace end (Lc) 1 m, vertical distance from running position of strand of introduction part to ceiling ( Ha) increases linearly from 0.1 m to 0.3 m in the running direction of the strand, and the length in the longitudinal direction of the strand introduction part (A) is 1/12 of the total length of the carbon fiber firing furnace. A thing was used. The carbonization temperature was 800 ° C. The generated gas in the carbon fiber firing furnace 2 was directed to the exhaust port 10 without being partially retained in the carbon fiber firing furnace for a long period of time, and was discharged out of the system through the exhaust port 10.

  As a result of continuous carbonization under these conditions for two months, stable carbonization could be performed without causing strand contamination, cutting, and deterioration. After continuous operation for two months, the operation was stopped and the inside of the carbon fiber firing furnace 2 was inspected. As a result, the deposition of solid-liquid mixed foreign matters on the ceiling 12 of the strand introduction part (A) and the carbonization main part (B) in the carbon fiber firing furnace was extremely slight.

(Example 2)
In the carbon fiber firing furnace shown in FIG. 5, the acrylic fiber strand 4 to which silicone oil was added as an oil treatment sizing agent in an amount of 1% by mass to the strand was supplied at a supply rate of 1.5 kg / min for carbonization. .

  The specifications of the carbon fiber firing furnace are as follows: total length of carbon fiber firing furnace (Lt) 15m, total height of carbon fiber firing furnace (Ht) 0.4m, total width of carbon fiber firing furnace (Wt) 1.6m, strand introduction part ( A) length (La) 1 m, carbonization main portion (B) length (Lb) 13 m, strand take-out portion (D) length (Ld) 1 m, length from exhaust port end to carbon fiber firing furnace end (Lc) 2 m, exhaust port length (Le) 1 m, vertical distance (Ha) from the running position of the strand of the introduction part to the ceiling 12 from 0.1 m to 0.3 m in the running direction of the strand The straight line gradually increases, the vertical distance (Hd) from the running position of the strand at the take-out part to the ceiling 16 gradually decreases linearly from 0.3 m to 0.1 m in the running direction of the strand. (A) and strike The longitudinal length of the command takeout part (D) was used as the 1/15 carbon fiber firing furnace length. Nitrogen gas was supplied from the inert gas inlet 18 as an inert gas, and the carbonization temperature was set to 800 ° C. The generated gas in the carbon fiber firing furnace 2 was directed to the exhaust port 10 without being partially retained in the carbon fiber firing furnace for a long period of time, and was discharged out of the system through the exhaust port 10.

  As a result of continuous carbonization under these conditions for two months, stable carbonization could be performed without causing strand contamination, cutting, and deterioration. After continuous operation for two months, the operation was stopped and the inside of the carbon fiber firing furnace 2 was inspected. As a result, the deposition of solid-liquid mixed foreign matter on the ceiling 12 of the strand introduction part (A), the ceiling 14 of the carbonization main part (B) and the ceiling 16 of the strand extraction part (D) in the carbon fiber firing furnace is extremely slight. Met.

(Comparative Example 1)
Carbonization was performed in the same manner as in Example 2 except that the carbon fiber firing furnace shown in FIG. 6 was used. The carbon fiber firing furnace used was the same as in Example 2 in terms of overall length, overall height, and overall width. The strand 34 was introduced from the strand inlet 36 and heat treated in the carbon fiber firing furnace 32a, and then the strand 34 was taken out from the strand outlet 38. During this time, nitrogen gas was supplied from the inert gas inlet 48 as an inert gas, and was discharged from the exhaust port 40 through a path as shown by the inert gas path 54. The generated gas 52 was discharged from the exhaust port 40 through a path as indicated by a generated gas path 56. When one week passed from the start of the operation of the carbon fiber firing furnace, a trouble of dropping the solid-liquid mixed foreign matters (72, 74) onto the strands 34 occurred. Furthermore, when one week passed, the strands were frequently contaminated, cut and deteriorated, and stable carbonization could not be performed. At this point, the operation was stopped and the inside of the carbon fiber firing furnace 32 was inspected. As a result, solid-liquid mixed foreign matter accumulated on the ceiling 62 on the strand inlet side, the inner wall 64 and the ceiling 66 on the strand outlet side, and the inner wall 68 (62a, 64a, 66a and 68a) were observed in large quantities, and traces of part of the deposits were observed at each location.

It is the schematic which shows an example of the carbon fiber baking furnace of this invention. It is the schematic which shows another example of the carbon fiber baking furnace of this invention. It is the schematic which shows another example of the carbon fiber baking furnace of this invention which provided the inert gas inlet_port | entrance. It is the schematic which shows an example of the carbon fiber baking furnace used for Example 1 of this invention, (I) shows a front view, (II) shows a top view. It is the schematic which shows an example of the carbon fiber baking furnace used for Example 2 of this invention, (I) shows a front view, (II) shows a top view. It is the schematic which shows an example of the conventional carbon fiber baking furnace, (I) shows the state of a generated gas flow, (II) shows the adhesion state, the fallen state, etc. of foreign materials, such as a powder, a crack, and a tar.

Explanation of symbols

2 Carbon fiber firing furnace 2a Firing chamber 4 Strand 4a Strand path 6 Strand inlet 8 Strand outlet 10 Exhaust port 12 Ceiling of strand introducing portion (A) 14 Ceiling of main portion (B) 16 Strand extracting portion (D) Ceiling 18 Inert gas inlet 22 Generated gas 24 Passage of inert gas 26 Generated gas path 32 Carbon fiber firing furnace 32a Inside of carbon fiber firing furnace 34 Strand 34a Strand path 36 Strand inlet 38 Strand outlet 40 Exhaust port 44 Carbon Fiber firing furnace ceiling 48 Inert gas inlet 52 Generated gas 52a Retained gas at strand inlet 52c Retained gas at strand outlet 54 Inert gas path 56 Generated gas path 62 Strand inlet side ceiling 62a Strand inlet side ceiling Solid-liquid mixture deposited on Foreign matter 64 Inner wall on the strand inlet side 64a Solid-liquid mixed foreign matter deposited on the inner wall on the strand inlet side 66 Ceiling on the strand outlet side 66a Solid-liquid mixed foreign matter deposited on the ceiling on the strand outlet side 68 Inner wall on the strand outlet side 68a On the strand outlet side Solid-liquid mixed foreign matter deposited on inner wall 72 Solid-liquid mixed foreign matter dropped on strand 74 Solid-liquid mixed foreign matter dropped on strand A A Strand introduction part B Carbonization main part D Strand extraction part La Length of strand introduction part Lb Carbon Ld Length of strand extraction part Lc Length from exhaust port end to carbon fiber firing furnace end Le Length of exhaust port part Lt Overall length of carbon fiber firing furnace Wt Full width of carbon fiber firing furnace Ha Introduced part Vertical distance from the running position of the strand to the ceiling Hb Height from Portland travel position from the travel position of the strands of the vertical distance Hd takeout part of the ceiling of the vertical distance Ht carbon fibers fired furnace ceiling

Claims (6)

In a carbon fiber firing furnace for carbonizing a flame-resistant fiber strand running in a carbon fiber firing furnace horizontally and parallel to the length direction of the carbon fiber firing furnace in an inert gas atmosphere, the carbon fiber firing furnace is ( A) A strand introduction part in which the ceiling height gradually increases in the strand running direction at a length of 1/50 to 1/10 of the length of the carbon fiber firing furnace from the strand inlet end of the carbon fiber firing furnace,
(B) The main body part formed continuously from the strand introduction part (A) and having a ceiling height in the direction of running of the strand and (C) the exhaust provided on the ceiling of the carbonization main part (B) And a carbon fiber firing furnace having a port. In a carbon fiber firing furnace for carbonizing a flame-resistant fiber strand running in a carbon fiber firing furnace horizontally and parallel to the length direction of the carbon fiber firing furnace in an inert gas atmosphere, the carbon fiber firing furnace is ( A) A strand introduction part in which the ceiling height gradually increases in the strand running direction at a length of 1/50 to 1/10 of the length of the carbon fiber firing furnace from the strand inlet end of the carbon fiber firing furnace,
(B) The main body portion formed following the strand introduction portion (A), the ceiling height of which is constant toward the strand running direction,
(C) An exhaust port provided on the ceiling of the carbonized main part (B) and (D) a carbon fiber fired formed following the main part (B) and formed from the main part rear end to the strand outlet end. A carbon fiber firing furnace having a length of 1/50 to 1/10 of the total length of the furnace and a strand take-out portion in which the ceiling height gradually decreases in the strand running direction. The carbon fiber firing furnace according to claim 1 or 2, wherein an inert gas introduction part (E) is provided below the strand introduction part (A). The carbon fiber baking furnace of Claim 1 or 2 which provided the exhaust port (C) in the ceiling of the strand exit side end part of the carbonization main part (B). The carbon fiber firing furnace according to claim 1 or 2, wherein a gradual increase in the ceiling height of the strand introduction portion (A) is linear. The carbon fiber firing furnace according to claim 2, wherein the gradual decrease in the ceiling height of the strand take-out portion (D) is linear.

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