JP2012207323A - Carbonization furnace and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbonization furnace which exhausts thermal decomposition gas smoothly; and a method for operating the same.SOLUTION: A carbonization furnace 1 comprises two side walls 5 and 6 facing each other which are formed along a traveling direction of oxidized fiber formed by carbonizing flame-resistant fiber F in a furnace. One or more exhaust ports 15 and 16 provided in the side walls 5 and 6 are biased to a side of an exit wall 4 in a furnace longitudinal direction and to a region higher than a traveling height of the oxidized fiber. A distance from an exit wall side end of the side walls to an exit wall side end of the exhaust ports is within a range of 20% of the furnace length of the carbonization furnace 1 in the furnace longitudinal direction.

Description

  The present invention relates to a carbonization furnace for firing and carbonizing flame-resistant fibers in the production of carbon fibers.

  Pitch-based and polyacrylonitrile (PAN) -based carbon fibers can be produced by firing and carbonizing flame-resistant fibers.

  The flameproof fiber is obtained by firing bundled raw material fibers in a strand form while stretching or shrinking in an oxidizing atmosphere of 200 to 300 ° C. The carbon fiber is produced by introducing the flameproof fiber into a carbonization furnace at 400 ° C. or higher in an inert gas atmosphere and firing it.

  As a conventional carbonization furnace, a carbonization furnace having a rectangular parallelepiped furnace body is known. FIG. 2 is a view showing an example of a conventional carbonization furnace, in which (A) is a plan view thereof, (B) is a side view thereof, and (C) is a front view thereof. According to FIG. 2, the furnace body 2 of the carbonization furnace 1 ′ includes an inlet wall 3 into which the flameproof fiber F is introduced into the furnace, and a flameproof fiber introduced from the inlet wall 3 so as to face the inlet wall 3. The carbon fiber G produced | generated by carbonizing F is provided with the exit wall 4 from which it discharges | emits out of a furnace.

  The flameproof fiber F is introduced from an inlet 3 a provided in the inlet wall 3. The flameproof fiber F introduced into the furnace is carbonized while running horizontally in the furnace. The carbonization treatment is performed in multiple stages as necessary. For example, after the first carbonization treatment is performed at 400 to 800 ° C. in an inert gas atmosphere, the second carbonization treatment is performed at 1000 ° C. or more. The The carbon fiber G obtained by the carbonization treatment is discharged from the outlet 4a provided on the outlet wall 4 to the outside of the carbonization furnace 1 '.

  By the carbonization treatment, 10 to 40% by mass of the flameproof fiber F is gasified to generate pyrolysis gas such as hydrogen cyanide, ammonia, carbon monoxide, carbon dioxide, methane, vaporized tar and the like.

  The pyrolysis gas containing vaporized tar and the like spreads inside the furnace body 2 along the traveling direction of the oxidized fiber formed by oxidizing the flameproof fiber F. Exhaust ports 15 and 16 are provided in the upper wall 8 of the furnace body 2. Exhaust ducts 13a and 13b are connected to the exhaust ports 15 and 16 via connection ducts 12a and 12b. In-furnace gas including pyrolysis gas passes through the connection ducts 12a and 12b and the exhaust ducts 13a and 13b from the exhaust ports 15 and 16, and is discharged out of the furnace.

  However, it is difficult to completely discharge a large amount of pyrolysis gas, and a part of the pyrolysis gas stays in the furnace. The staying pyrolysis gas touches the inner wall and the like of the carbonization furnace, and a part of it condenses to become a liquid foreign substance such as tar and adheres to the inner wall of the carbonization furnace 1 ′.

  When the flameproof fiber F is oil-treated with a sizing agent such as silicone oil, the silicone oil or the like is thermally decomposed to generate solid foreign matters such as silica powder. A part of the solid foreign matter adheres to the surface of the liquid foreign matter that adheres to the inner wall of the carbonization furnace. As a result, solid-liquid mixed foreign matter including liquid foreign matter such as tar and solid foreign matter such as silica powder is deposited on the inner wall of the carbonization furnace 1 ′.

  The solid-liquid mixed foreign matter deposited on the inner wall becomes high density as the amount of deposition increases. When a certain amount of high-density solid-liquid mixed foreign matter accumulates on the inner wall of the upper wall 8 in particular, the solid-liquid mixed foreign matter falls from the inner wall of the upper wall 8 onto the flame-resistant fiber F traveling in the furnace, and becomes flame resistant. The fiber F is contaminated. Moreover, the solid-liquid mixed foreign material dropped on the flame resistant fiber F not only deteriorates the quality of the flame resistant fiber F but also may cut the flame resistant fiber F. That is, the accumulation of solid-liquid mixed foreign matter on the inner wall of the carbonization furnace 1 ′ causes a reduction in the product rate.

  In order to solve such a problem of flame resistant fiber fouling, various solving means have been proposed (see, for example, Patent Documents 1 and 2).

  The carbonization furnace disclosed in Patent Document 1 is provided with a plurality of exhaust ports or slit-shaped exhaust ports on the upper wall. In this carbonization furnace, the exhaust port is arranged at a position where the temperature setting in the furnace reaches the maximum temperature, etc., and the front and rear corners in the fiber running direction of the exhaust port are formed in an arc shape, so that Guide the gas to the exhaust.

  However, since this carbonization furnace is provided with an exhaust port at a position where the most amount of tar component is generated, the tar component tends to adhere to the vicinity of the exhaust port on the upper wall. Therefore, it is necessary to clean the exhaust port frequently.

Patent Document 2 discloses a carbonization furnace that carbonizes a flame-resistant fiber bundle sheet in which a plurality of flame-resistant fiber bundles are arranged in a sheet shape. The exhaust port of the carbonization furnace is provided at a position other than the upper position in the direction perpendicular to the traveling direction of the flameproof fiber bundle sheet, specifically, at the lower wall. Even in such a structure, the pyrolysis gas staying on the upper wall side of the carbonization furnace is not completely absent.
JP 2002-294521 A (Claims) JP 2007-262602 A (Claims)

  The present inventor considered that adhesion of tar components and the like to the inner wall surface of the furnace was caused by residence of pyrolysis gas generated with the carbonization treatment in the furnace. The object of the present invention is to improve the exhaustability of the pyrolysis gas generated by the carbonization treatment, improve the residence state of the pyrolysis gas in the furnace, and by the solid-liquid mixed foreign matter generated by the carbonization treatment An object of the present invention is to provide a carbonization furnace for preventing flame-resistant fiber contamination and an operation method thereof.

The present invention for achieving the above object is described below.
[1] An inlet wall having an inlet through which flame-resistant fibers are introduced into the furnace, and carbon fibers generated by carbonizing the flame-resistant fibers in the furnace facing the inlet wall are discharged to the outside of the furnace. And an upper wall and a bottom formed along a traveling direction in which oxidized fibers formed by oxidizing the flameproof fibers in the furnace travel in the furnace length direction from the inlet toward the outlet. An internal hollow carbonization furnace having a wall and two side walls facing each other formed along a running direction of the oxidized fiber, wherein each side wall has one or more exhaust ports, In the furnace length direction, provided on the outlet wall side and biased in a region higher than the running height of the oxidized fiber, the outlet wall side end portion of the exhaust port and the outlet wall side end portion of the side wall, Carbonization in which the distance in the furnace length direction is within 20% of the furnace length of the carbonization furnace .
[2] A connection duct connected to one end portion in the longitudinal direction is connected to the periphery of the exhaust port, and an adjustment valve for adjusting the flow rate of the in-furnace gas is attached to the exhaust port or the connection duct. The carbonization furnace of [1].
[3] The carbonization furnace according to [2], wherein a cross-sectional shape of one end portion of the connection duct connected to a peripheral edge of the exhaust port is the same as the shape of the exhaust port.
[4] The connection duct is installed such that the other end opposite to the one end is higher than the one end, and an inclination angle with respect to the bottom wall is 20 ° to 60 °. A certain [2] or [3] carbonization furnace.
[5] The method for operating a carbonization furnace according to [1], wherein a duct for discharging the gas in the furnace containing the pyrolysis gas generated by carbonizing the flame resistant fiber to the outside of the furnace is connected, A method for operating a carbonization furnace, wherein the average flow velocity of the in-furnace gas passing through the duct is controlled to 10 to 20 m / sec.

  The carbonization furnace of this invention improves the residence state in the furnace of the pyrolysis gas generated with the carbonization process of a flameproof fiber. As a result, the present invention reduces the amount of pyrolysis gas components staying in the furnace as solid-liquid mixed foreign matter and deposits on the inner wall surface of the furnace, and makes the solid-liquid mixed foreign material flame resistant from the inner wall of the carbonization furnace. It can prevent falling on a fiber and fouling a flame-resistant fiber. As a result, the product rate of good quality carbon fibers can be improved.

  Hereinafter, the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic view showing an example of a carbonization furnace of the present invention, (A) is a plan view thereof, (B) is a side view thereof, and (C) is a front view thereof. . The portions in common with the conventional carbonization furnace 1 ′ shown in FIG. 2 are used as they are. In FIG. 1 (A) and FIG. 1 (B), the part which is shielded by the furnace wall of the flameproof fiber F and cannot be visually recognized is indicated by a dotted line to make it easy to understand the running state of the flameproof fiber F in the furnace. In the following description, the “flame-resistant fiber” may mean an oxidized fiber obtained by oxidizing the flame-resistant fiber F in the furnace body 2.

  In the furnace main body 2 of the carbonization furnace 1, the distance between the inlet wall 3 into which the flameproof fiber F is introduced into the furnace and the outlet wall 4 facing the inlet wall 3 is a furnace length Lt. The distance between the side wall 5 and the side wall 6 facing each other with the flameproof fiber F traveling from the inlet wall 3 toward the outlet wall 4 is defined as a furnace width Lw. The furnace body 2 may have any shape as long as it is a known shape, but as a general shape, FIG. 1 shows a rectangular parallelepiped furnace body 2 having a furnace length Lt longer than the furnace width Lw.

  The inlet wall 3 is provided with an inlet 3a at which a flameproof fiber F is introduced into the furnace at a central portion in the furnace height (Hf) direction perpendicular to the bottom wall 7. A portion of the outlet wall 4 corresponding to the inlet 3a is provided with an outlet 4a for discharging the carbon fiber G generated by carbonizing the flameproof fiber F in the furnace to the outside of the furnace. Examples of the shapes of the inlet 3a and the outlet 4a include slit shapes that are long in the furnace width Lw direction.

  When carbonizing the flameproof fiber strands F of the yarn, a plurality of flameproof fiber strands F (eight in FIG. 1) are arranged in the furnace width Lw direction. The flameproof fiber strand F introduced into the furnace from the inlet 3a travels in the furnace length Lt direction from the inlet 3a to the outlet 4a. The traveling direction is parallel to the bottom wall 7 of the furnace body and parallel to the side walls 5 and 6 of the furnace body 2.

  The flame resistant fiber strand F is fired and carbonized in an inert gas atmosphere such as nitrogen gas while running in the furnace. The firing temperature is 400 ° C. or higher.

  The carbonization treatment may be performed in a two-stage carbonization furnace. The first first carbonization furnace is heated to 400 to 800 ° C. from the inlet wall side toward the outlet wall side. The firing temperature of the second carbonization furnace at the latter stage is 1000 ° C. or higher. There is a tendency that a large amount of pyrolysis gas is generated in the temperature range of the first carbonization furnace. Therefore, the carbonization furnace 1 of the present invention is preferably used as the first carbonization furnace.

  As the flameproof fiber strand F is carbonized, pyrolysis gas is generated in the furnace body 2. The pyrolysis gas flows along the traveling direction of the flameproof fiber strand F, that is, in the furnace length Lt direction from the inlet wall 3 side to the outlet wall 4 side. When the pyrolysis gas reaches the inner wall of the outlet wall 4, the pyrolysis gas further travels along the inner wall of the outlet wall 4 toward the inner walls of the upper wall 8 and the side walls 5 and 6. In the above-described flow of pyrolysis gas, when a large amount of pyrolysis gas is generated, the corner wall 9a where the inner wall of the outlet wall 4, the inner wall of the upper wall 8, and the inner wall of the side wall 5 contact, or the inner wall of the outlet wall 3 and the upper wall. The pyrolysis gas tends to stay in the corner portion 9b where the inner wall 8 and the inner wall of the side wall 6 are in contact. The “corner portion” means a region where the inner wall of the outlet wall 3, the inner wall of the upper wall 8, the inner wall of the side wall 5, or the inner wall of the side wall 6 is in contact with the region.

  In the present invention, one or more exhaust ports 10 and 11 are provided on the side wall 5 side of the corner portion 9a and on the side wall 6 side of the corner portion 9b, respectively.

  The exhaust ports 10 and 11 are provided biased in a region higher than the traveling height R of the flameproof fiber strand F on the outlet wall 4 side in the furnace length Lt direction. The exhaust ports 10 and 11 have a distance Ls (not shown) in the furnace length Lt direction between the outlet wall 4 side end and the side walls 5 and 6 on the outlet wall 4 side, respectively. It is preferable to be provided so as to be within 20% of the length Lt.

  Thus, in the present invention, the gas flow of the furnace gas toward the inner wall of the upper wall 8 and the side walls 5 and 6 along the inner wall of the outlet wall 4 naturally goes to the exhaust ports 10 and 11. Therefore, the furnace gas that has reached the inner wall of the outlet wall 4 can be quickly discharged from the exhaust ports 10 and 11 before reaching the inner wall of the upper wall 8, and the gas in the furnace at the corners 9a and 9b can be easily The residence state can be improved.

  FIG. 1B illustrates the side wall 5 in which one exhaust port 10 is provided. 1B, the outlet wall 4 side end portion 10a of the exhaust port 10 is closest to the outlet wall 4 side of the side wall 5, that is, from the outlet wall 4 side end portion 5a of the side wall 5 to the exhaust port 10 side. A distance Ls (not shown) to the outlet wall 4 side end 10 a is 0% of the furnace length Lt of the carbonization furnace 1. The upper wall 8 side end portion 10 b of the exhaust port 10 is located on the uppermost wall 8 side of the side wall 5. The exhaust port 10 is biased toward the outlet wall 4 side in the furnace length Lt direction and in a region higher than the traveling height R of the flameproof fiber F in the furnace height Hf direction.

  The length of the exhaust port 10 in the furnace length Lt direction is not particularly limited, but is preferably provided as appropriate within a range of 5 to 20% of the entire furnace length Lt of the furnace body 2. If it is shorter than 5%, the exhaust port 10 becomes small, so there is a possibility that exhaust gas cannot be discharged sufficiently. When the length exceeds 20%, the exhaust port 10 may not be biased toward the outlet wall 4 side depending on the position of the outlet wall 4 side end portion 10a of the exhaust port 10. In that case, the in-furnace gas cannot be exhausted intensively at the corner 9a, and the in-furnace gas that cannot be exhausted may stay in the corner 9a, or from the corner 9a toward the upper wall 8. May spread.

  Although not shown, an exhaust port 11 is similarly provided on the side wall 6 side of the corner portion 9b. The exhaust port 10 provided in the side wall 5 and the exhaust port 11 provided in the side wall 6 are preferably provided at positions corresponding to each other.

  According to FIG. 1 (A) and FIG. 1 (C), one end in the longitudinal direction of the connection ducts 12a and 12b is connected to the peripheral edges of the exhaust ports 10 and 11, respectively. Exhaust ducts 13 a and 13 b are connected to the other end opposite to the one end connected to the exhaust ports 10 and 11. The in-furnace gas including the pyrolysis gas discharged from the exhaust ports 10 and 11 passes through the connection ducts 12a and 12b and the exhaust ducts 13a and 13b, and is sent to a pyrolysis gas processing apparatus (not shown).

  The flow rate of the in-furnace gas passing through the connection ducts 12a and 12b is adjusted using the adjustment valves 14a and 14b. As the regulating valves 14a and 14b, known ones can be used, and those capable of adjusting the opening ratio of the exhaust port are preferable.

  In addition to being attached to the exhaust ports 10 and 11, the regulating valve is preferably attached to any position on the side connected to the periphery of the exhaust ports 10 and 11 in the longitudinal direction of the connection ducts 12a and 12b.

  The opening ratio of the regulating valve is preferably adjusted within a range of 70 to 100% and more preferably adjusted within a range of 80 to 100% during operation.

  The average flow velocity of the in-furnace gas passing through the connection ducts 12a and 12b is controlled according to the amount of pyrolysis gas generated. The average flow rate is preferably 10 to 20 m / second, more preferably 15 to 20 m / second. If the average flow rate is slower than 10 m / sec, the pyrolysis gas may stay in the furnace body 2. The average flow rate of the in-furnace gas is preferably controlled by adjusting the flow rate of the in-furnace gas using the regulating valves 14a and 14b attached to the exhaust ports 10 and 11 and the like.

  Although the shape of the exhaust ports 10 and 11 is not specifically limited, When adjusting an aperture ratio using the regulating valves 14a and 14b, it is preferable that it is a rectangle from a viewpoint of ease.

  The cross-sectional shape of the end portion of the connection ducts 12a and 12b connected to the exhaust ports 10 and 11 is preferably matched with the shape of the exhaust ports 10 and 11 in order to maintain airtightness.

  The type of the connection ducts 12a and 12b is not particularly limited, but when the shape of the exhaust ports 10 and 11 is a rectangle, a rectangular tube is selected as the connection ducts 12a and 12b having a corresponding connection cross section. It is preferred that

  The dimensions of the exhaust port 10 and the exhaust port 11 are preferably the same from the viewpoint of easily adjusting the flow rate of the in-furnace gas.

  The connection ducts 12a and 12b are installed so that the other end on the side opposite to the one connected to the peripheral edge of the exhaust ports 10 and 11 in the longitudinal direction is higher than the one end. . The inclination angles of the connection duct 12a and the bottom wall 7 are each preferably 20 ° to 60 °, and more preferably 30 ° to 60 °. The inclination angle between the connection duct 12b and the bottom wall 7 preferably matches the inclination angle of the connection duct 12a.

  The exhaust ducts 13 a and 13 b are connected to the furnace body 2 via connection ducts 12 a and 12 b connected to the furnace body 2. As shown in FIGS. 1 (A) and 1 (C), the exhaust duct 13a is disposed above the upper wall 8 of the furnace body 2 and outside the side wall 5, and the exhaust duct 13b is disposed on the upper wall of the furnace body 2. 8 and on the outside of the side wall 6.

  By installing the connection ducts 12a and 12b at the above-described inclination angle, the exhaust ports 10 and 11 of the furnace body 2 and the exhaust ducts 13a and 13b can be connected in the shortest distance. Thereby, the in-furnace gas discharged from the exhaust ports 10 and 11 can be quickly exhausted into the exhaust ducts 13a and 13b.

  When the connection ducts 12a and 12b are installed outside the range of the above inclination angles, the passage route of the gas discharged to the outside of the furnace is detoured, so in the middle of the connection ducts 12a and 12b and the exhaust ducts 13a and 13b There is a possibility that the gas stays and hinders the smooth discharge of the pyrolysis gas.

  The temperature in the connecting ducts 12a and 12b is preferably 200 ° C. or higher. When the temperature is lower than 200 ° C., the pyrolysis gas is cooled and condensed and solidified in the connection ducts 12a and 12b. In that case, the pyrolysis gas component condensed in the connection ducts 12a and 12b becomes a solid-liquid mixed foreign matter and may adhere to the connection ducts 12a and 12b or may block the exhaust ports 10 and 11. .

With the above configuration, the furnace gas including the pyrolysis gas generated in the furnace body 2 smoothly flows through the exhaust ports 10 and 11 before reaching the inner wall of the upper wall 8 of the furnace body 2 according to the formed gas flow. Exhausted from. By connecting the connection ducts 12a and 12b at a predetermined inclination angle and connecting the exhaust ports 10 and 11 and the exhaust ducts 13a and 13b with the shortest distance, the furnace gas containing the pyrolysis gas is exhausted more smoothly. be able to.
By smoothly exhausting the in-furnace gas, the pyrolysis gas contained in the in-furnace gas is less likely to touch the inner wall of the furnace body 2, and the inner wall of the solid-liquid mixed foreign material derived from the pyrolysis gas, particularly the upper The amount of deposition on the inner wall of the wall 8 can be reduced. As a result, contamination, cutting, and deterioration of the flame-resistant fiber strand due to the adhesion of the solid-liquid mixed foreign matter can be prevented, and the product rate of good quality carbon fibers can be improved.

  In the present invention, the arrangement, shape, and number of exhaust ports are not limited to those shown in FIG. FIG. 3 is another example of the carbonization furnace of the present invention, (A) is a plan view thereof, (B) is a side view thereof, and (C) is a front view thereof. The carbonization furnace 100 is provided with one elliptical exhaust ports 110 and 111 on the side walls 5 and 6, respectively, which are different from the exhaust ports 10 and 11 of FIG. 1.

  According to FIG. 3 (B), the exhaust ports 110 and 111 are biased toward the outlet wall 4 side in the furnace length Lt direction and in a region higher than the traveling height R of the flameproof fiber F. In the carbonization furnace 100, the outlet wall 4 side end portion 110 a of the exhaust port 110 is slightly separated from the outlet wall 4 side end portion 5 a of the side wall 5. The distance Ls from the outlet side 4 end portion 5 a of the side wall 5 to the outlet wall 4 side end portion 110 a of the exhaust port 110 is within 20% of the furnace length Lt of the carbonization furnace 100.

  FIG. 4 is still another example of the carbonization furnace of the present invention, (A) is a plan view thereof, (B) is a side view thereof, and (C) is a front view thereof. In the carbonization furnace 300 illustrated in FIG. 4, three exhaust ports 301, 302, and 303 are provided on the side wall 5, and three exhaust ports 304, 305, and 306 are provided on the side wall 6.

  According to FIG. 4B, exhaust ports 301, 302, 303 are arranged on the side wall 5 of the carbonization furnace 300 from the outlet wall 4 side toward the inlet wall 5 in the furnace length Lt direction. Is farthest from the end 5a of the side wall 5 on the outlet wall 4 side. The distance Ls from the outlet wall 4 side end portion 5 a of the side wall 5 to the outlet wall 4 side end portion 303 a of the exhaust port 303 is within 20% of the furnace length Lt of the carbonization furnace 300. Similarly, on the side wall 6, three exhaust ports 304, 305, 306 are arranged in the furnace length Lt direction.

Hereinafter, although the carbonization furnace of this invention is demonstrated using an Example and a comparative example, this invention is not limited to an Example.
[Example 1]
Carbon fiber was manufactured using the carbonization furnace 1 of the present invention shown in FIG. The outer dimensions of the furnace body 2 of the carbonization furnace 1 are a furnace width Lw of 4000 mm, a furnace length Lt of 7000 mm, and a furnace height Hf of 600 mm.

  A rectangular exhaust port 10 is provided on the side wall 5 side of the furnace body 2. The exhaust port 10 is biased most toward the outlet wall 4 side and the uppermost wall 8 side in the side wall 5. A distance Ls from the outlet wall 4 side end portion 5 a of the side wall 5 to the outlet wall 4 side end portion 10 a of the exhaust port 10 is 0% of the furnace length Lt of the carbonization furnace 1.

  The dimension of the exhaust port 10 is 600 mm (length in the furnace length Lt direction) × 150 mm (length in the furnace height Hf direction), and the length in the furnace length Lt direction is 8.6 of the furnace length Lt of the carbonization furnace 1. %.

  An exhaust port 11 having the same shape as the exhaust port 10 is provided at a position corresponding to the exhaust port 10 provided on the side wall 5 of the side wall 6.

  Exhaust ducts 13a and 13b are connected to the side walls 5 and 6 of the furnace body 2 via connection ducts 12a and 12b.

  The exhaust ducts 13a and 13b are round cylinders having a diameter of 300 mm. Above the upper wall 8 of the furnace body 2, the exhaust duct 13 a is installed outside the side wall 5, and the exhaust duct 13 b is installed outside the side wall 6, parallel to the traveling direction of the flameproof fiber strand F in the furnace body 2. The

  Each of the connection ducts 12a and 12b is a square tube having a cross-sectional dimension of 600 mm × 150 mm and a length of 2000 mm. Each connection duct 12a has one end in the longitudinal direction connected to the periphery of the exhaust port 10 without a gap. Each connecting duct 12a is installed at an angle of 30 ° with respect to the bottom wall 7 so that the other end opposite to the one end is higher than the one end. The other end is connected to the exhaust duct 13a. The connection duct 12b is also installed in the same manner, and the exhaust duct 13b is connected to the exhaust port 11.

  The connection ducts 12 a and 12 b include dampers 14 a and 14 b in the vicinity of one end connected to the peripheral edges of the exhaust ports 10 and 11. The dampers 14a and 14b adjust the flow rate of the pyrolysis gas in the connection ducts 12a and 12b. In this example, the opening ratios of the exhaust ports 10 and 11 were adjusted to 80% by the dampers 14a and 14b, and the average flow rate of the pyrolysis gas in the connection ducts 12a and 12b was set to 10 to 15 m / sec.

  The temperatures in the connection ducts 12a and 12b and the exhaust ducts 13a and 13b were 250 ° C. or higher.

  In the carbonization furnace 1 having the above-described configuration, a 14-day operation was performed at a line speed of 150 m / hour and a production amount of 0.4 t / day to obtain carbon fibers of good quality. The pyrolysis gas generated at this time entered the connection ducts 12a and 12b through the exhaust ports 10 and 11, and was further discharged as exhaust gas through the exhaust gas ducts 13a and 13b.

  After the operation for 14 days, there was almost no adhesion of foreign matters such as tar and silica powder in the furnace body 2, the connection ducts 12a and 12b, and the exhaust gas ducts 13a and 13b.

Regarding the product rate of good quality carbon fibers, carbon fibers with less than 0.5 contamination spots due to solid-liquid mixed foreign matter per 100 m length of 10 bundles of carbon fiber strands are defined as good quality carbon fibers. The mass ratio of the good quality carbon fiber to the total amount of carbon fiber produced was evaluated. The product rate of this example was 97%.
[Comparative Example 1]
Carbon fiber was manufactured using the carbonization furnace 1 'shown in FIG. The outer dimensions of the furnace body 2 of the carbonization furnace 1 ′ are a furnace width Lw of 4000 mm, a furnace length Lt of 7000 mm, and a furnace height Hf of 600 mm.

  The upper wall 8 of the furnace body 2 is provided with circular exhaust ports 15 and 16 having a diameter of 300 mm. The exhaust ports 15 and 16 each have a circle center 300 mm inside from the outlet wall 4 side end 8a of the upper wall 8, and are arranged in a line in the furnace width Lw direction. The exhaust port 15 has a circular center provided 1000 mm inside from the side wall 5 side end portion 8 b of the upper wall 8. The exhaust port 16 is provided such that the center of the circle is 1000 mm inside from the side wall 6 end 8 c of the upper wall 8.

  Exhaust ducts 13a and 13b are connected to the upper wall 8 of the furnace body 2 via connection ducts 12a and 12b.

  Each exhaust duct 13a, 13b is a round cylinder having a diameter of 300 mm. The exhaust duct 13a is installed in a region overlapping the exhaust port 15 above the upper wall 8 of the furnace body 2 in parallel with the traveling direction of the flameproof fiber strand F in the furnace body 2. Similarly, the exhaust duct 13 b is installed in a region overlapping the exhaust port 16.

  Each connection duct 12a, 12b is a cylinder having a diameter of 300 mm and a length of 1000 mm. In the positional relationship between the furnace body 2 and the exhaust ducts 13a and 13b, the connection ducts 12a and 12b are installed at an inclination angle of 90 ° with respect to the bottom wall 7 of the furnace body 2.

  In the carbonization furnace 1 ′ having the above-described configuration, the same operation as that of the example was performed for 14 days to obtain a carbon fiber having a good quality. The pyrolysis gas generated at this time entered the connection ducts 12a and 12b from the exhaust ports 15 and 16, and was further discharged as exhaust gas through the exhaust gas ducts 13a and 13b.

After the operation for 14 days, foreign matter such as tar and silica powder was observed in the furnace body 2, the connection ducts 12a and 12b, and the exhaust gas ducts 13a and 13b. The product rate was 92%.
[Comparative Example 2]
The carbonization furnace used in Comparative Example 2 is the same as the carbonization furnace used in Example 1, except that the distance Ls in the furnace length direction between the outlet face side end of the exhaust port and the outlet face side end of the side wall is small. The difference is that it is 1450 mm. This distance Ls (1450 mm) is 20.7% of the furnace length Lt (7000 mm), and the exhaust port is provided at a position away from the outlet wall side as compared with the carbonization furnace of Example 1.

The operation was carried out under the same conditions as in Example 1 using the above carbonization furnace. After the operation for 14 days, tar adhesion was observed in the furnace body 2 and in the connection ducts 12a and 12b. The product rate was 92%.
[Comparative Example 3]
The operation was performed under the same conditions as in Example 1 except that the connecting ducts 12a and 12b were installed at an inclination angle of 15 ° with respect to the bottom wall 7.

  After the operation for 14 days, tar adhesion was observed in the furnace body 2 and in the connection ducts 12a and 12b. The product rate was 94%.

  In Comparative Examples 1 to 3 shown above, tar adhesion was observed in the furnace. In each comparative example, the reason why the product rate was lower than that of the example is presumed that the tar adhering to the inner wall of the carbonization furnace fell on the flameproof fiber running in the furnace.

It is the schematic which shows an example of the carbonization furnace of this invention, (A) is the top view, (B) is the side view, (C) is the front view. It is the schematic which shows an example of the conventional carbonization furnace, (A) is the top view, (B) is the side view, (C) is the front view. It is the schematic which shows another example of the carbonization furnace of this invention, (A) is the top view, (B) is the side view, (C) is the front view. It is the schematic which shows another example of the carbonization furnace of this invention, (A) is the top view, (B) is the side view, (C) is the front view. .

DESCRIPTION OF SYMBOLS 1 Carbonization furnace 1 'Carbonization furnace 2 Furnace main body 3 Furnace main body entrance wall 3a Inlet 4 Furnace main body exit wall 4a Outlet 5, 6 Furnace main body side wall 5a Side wall outlet wall side edge 5b Side wall upper wall side edge Part 7 Bottom wall of furnace body 8 Upper wall of furnace body 8a Exit wall side end part of upper wall 8b, 8c Side wall side end part of upper wall 9a, 9b Corner part 10, 11 Exhaust port 10a Exit wall side end of exhaust port Part 10b Upper wall side end of exhaust port 12a, 12b Connection duct 13a, 13b Exhaust duct 14a, 14b Damper (regulating valve)
15, 16 Exhaust port 100 Carbonization furnace 110, 111 Exhaust port 110a End wall side end of exhaust port 300 Carbonization furnace 301, 302, 303, 304, 305, 306 Exhaust port 303a Outlet wall side end of exhaust port 303 Lt Carbonization furnace length Lw Carbonization furnace width Hf Carbonization furnace height Ls Distance from outlet wall side end of side wall to outlet wall side end of exhaust outlet

Claims (5)

  An inlet wall having an inlet through which the flame resistant fiber is introduced into the furnace, and an outlet facing the inlet wall, and the carbon fiber generated by carbonizing the flame resistant fiber in the furnace is discharged to the outside of the furnace. An exit wall provided, and an upper wall and a bottom wall formed along a traveling direction in which oxidized fibers formed by oxidizing the flameproof fiber in the furnace travel in the furnace length direction from the inlet toward the outlet, and An internal hollow carbonization furnace having two side walls opposed to each other formed along the running direction of the oxidized fiber, wherein one or more exhaust ports are provided in the side of the furnace. The furnace length direction of the outlet wall side end portion of the exhaust port and the outlet surface side end portion of the side wall provided on the outlet wall side in the direction and biased to a region higher than the running height of the oxidized fiber The carbonization furnace whose distance in is within 20% of the furnace length of the said carbonization furnace.   A connection duct to which one end portion in the longitudinal direction is connected to a peripheral edge of the exhaust port, and an adjustment valve for adjusting a flow rate of in-furnace gas is attached to the exhaust port or the connection duct. Item 4. The carbonization furnace according to Item 1.   The carbonization furnace according to claim 2, wherein a cross-sectional shape of one end portion of the connection duct connected to a peripheral edge of the exhaust port is the same as the shape of the exhaust port.   The connection duct is installed such that the other end opposite to the one end is higher than the one end, and an inclination angle with the bottom wall is 20 ° to 60 °. The carbonization furnace of Claim 2 or Claim 3.   The operation method of the carbonization furnace according to claim 1, wherein a duct for discharging the gas in the furnace including the pyrolysis gas generated by carbonizing the flame resistant fiber to the outside of the furnace is connected. A method for operating a carbonization furnace, wherein an average flow velocity of the in-furnace gas passing through the inside is controlled to 10 to 20 m / sec.

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