JP2013091863A - Heat treatment furnace of fiber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment furnace of fiber sheet capable of uniforming the temperature distribution in a sheet width direction of a heat treatment chamber and enabling the reduction in cost necessary for uniforming the temperature distribution.SOLUTION: A heat treatment furnace comprises a heat treatment chamber of continuous fiber sheet in a hot air circulation path arranged in a horizontal space; and a heating device 18 of processing gas and a circulation fan arranged in the hot air circulation path outside the heat treatment chamber in this order in a flowing direction of hot air. In the heat treatment chamber, there is a fiber running path on which one or more pair of fiber sheets are running horizontally in parallel one above the other. The heating device 18 comprises: a gas heating region composing a processing gas heating surface 18a; and a gas non-heated region between the gas heating region and a frame 18b of the gas heating surface. At a position adjacent to the heating device 18, provided is a wind direction controlling member 20 for directing the flow of the processing gas, which passes through the gas non-heated region between a gas heating region edge on at least a floor side and the frame 18b, to the gas heating region.

Description

  The present invention relates to a heat treatment furnace for continuously performing various heat treatments on a fiber sheet, and particularly to a heat treatment furnace for a fiber sheet that can be suitably applied to a precursor fiber flameproofing furnace in a carbon fiber production process.

  Since carbon fibers are excellent in specific strength, specific elastic modulus, fire resistance, heat resistance, durability and the like, their application fields are expanding. The carbon fiber is manufactured by firing the precursor fiber, and the process includes a flame resistance process, a pre-carbonization process, and a carbonization process. In the flameproofing step, the precursor fiber is heat-treated in an oxidizing atmosphere to impart thermal stability to the precursor fiber. This flameproofing process is the most time-consuming process in the carbon fiber manufacturing process, and is greatly involved in the development of carbon fiber performance. Currently, there are temperature spots in the width direction in a flameproofing furnace in a carbon fiber manufacturing factory that is in operation, and thus there are firing spots on the carbon fibers. From the viewpoint of uniforming the quality of carbon fiber and improving yield, it is required to make the temperature distribution in the flameproofing furnace uniform.

  Specific proposals for equalizing the temperature distribution in the flameproofing furnace and eliminating temperature spots are disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-088464 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2001-288623 (Patent Document 2). ), JP-A-2003-155629 (Patent Document 3), JP-A-2008-138325 (Patent Document 4), JP-A-2008-280640 (Patent Document 5), and the like. In addition, proposals for uniforming the wind speed and temperature distribution in the flameproofing furnace have been made by, for example, Japanese Unexamined Patent Application Publication No. 2007-247130 (Patent Document 6) and Japanese Unexamined Patent Application Publication No. 2008-267794 (Patent Document 7). Yes.

  Specifically, in Patent Document 1, a hot air blowing nozzle covered with a heat insulating material is provided in the vicinity of the fiber lead-in / out section in the heat treatment chamber to prevent heat dissipation, and at the same time, a heating means and a temperature control sensor are provided in the nozzle to be taken away. Replenishes the heat released. In patent document 2, the static mixer which is a hot air stirring apparatus is provided in the convection heating type hot air circulation path outside the heat treatment chamber, the pressure loss when passing through the static mixer is 3 Pa or more, In particular, by making the temperature distribution and gas concentration distribution uniform and eliminating the processing spots in the flameproofing process, the physical properties of the resulting continuous fiber bundle are made uniform and the production efficiency is improved.

  According to Patent Document 3, the furnace wall of the flameproofing furnace has a double structure to prevent temperature spots in the processing chamber due to heat dissipation of the furnace wall, and the wind direction protrudes from the double structure inner wall toward the yarn running direction. Conversion fins are provided to achieve uniform processing chamber temperature and increase production efficiency. In Patent Document 4, the temperature fluctuation in the furnace is suppressed to 3 ° C. or less by controlling the outside air temperature in the vicinity of the entrance / exit of the precursor fiber bundle of the flameproofing furnace.

  According to Patent Document 5, the first and second hot air circulation channels each provided with hot air blowing means are provided on both side walls in the width direction of the heat treatment chamber outside the heat treatment chamber. One end of the first hot air circulation nozzle is connected to one end of the second hot air circulation passage, and the other end of the first hot air circulation passage is connected to the first hot air suction nozzle. The other end of the flow path is connected to the second hot air suction nozzle, and both sides of the heat treatment chamber with respect to the yarn transfer direction are surrounded by the first and second circulation flow paths to prevent heat radiation to the outside of the heat treatment chamber and the width of the yarn. The distribution of the hot air temperature and the wind speed in the yarn width direction is made uniform by arranging the air in multiple stages on both sides in the direction and blowing the hot air alternately up and down for each stage.

Patent Documents 2, 3, 4, 6, and 7 have been proposed with the main purpose of making the temperature distribution in the heat treatment chamber uniform in the flameproofing path, as in Patent Documents 1 and 5, but none of them. Since the hot air is passed perpendicularly to the surface of the yarn sheet that is transferred in multiple stages, the yarn is entangled with the hot air, and damage such as yarn breakage and fluffing is likely to occur. In that respect, since the heat treatment furnaces of Patent Documents 1 and 5 flow hot air parallel to the traveling direction of the fiber sheet traveling in the heat treatment, the fiber sheet can be stably processed.

JP 2000-088464 A JP 2001-288623 A JP 2003-155629 A JP 2008-138325 A JP 2008-280640 A JP 2007-247130 A JP 2008-267794 A

  By the way, the flameproofing furnaces proposed by the above-mentioned Patent Documents 1 to 7 all have a processing gas flow path flowing in the furnace as a circulation flow path including a heat treatment chamber, and a circulation flow excluding the heat treatment chamber. A heating device and a circulation fan are arranged on the way. Under such circumstances, in Patent Document 2, a static mixer as a hot air stirring device is installed in a circulation channel between a heating device and a circulation fan. The static mixer, however, encourages mixing by twisting the channel in the horizontal and vertical directions, but the twist of the channel is such that the adjacent area separated by the mixing plate is replaced, and the processing gas in the entire channel is changed. It does not have a mixing effect. Therefore, gas is not stirred in the inner region near the heat treatment chamber in the width direction of the circulation channel and the outer region, and the gas flows between courses with little mixing of the gas between the respective regions. .

  This tendency is the same in the case where the stirring device is not provided and only the circulation fan is provided, and the inner region on the heat treatment chamber side in the width direction of the processing gas circulation channel and the outer region thereof. The temperature of the process gas flowing in the outer region is proved to be relatively lower than the temperature of the process gas flowing in the heat treatment chamber side region, and the temperature distribution of the process gas introduced into the heat treatment chamber at the same time is It has also been demonstrated that the high temperature region extends upward in the direction from below. FIG. 8 shows the temperature distribution in the rectification box inflow cross section when viewed from the hot air introduction section. The figure shows a state in which the transition from the high temperature to the low temperature is performed from the dark color portion to the light color portion. As can be understood from FIG. 8, the high temperature region and the low temperature region have a distribution form that is diagonally divided into two by a straight line connecting the upper right corner and the lower left corner of the rectification box inflow cross section. That is, in the inflow cross-section of the rectification box, the high temperature region extends from the upper left corner to the upper right side, gradually expands from the upper left corner to the lower half along the left edge, and from the lower right corner to the left. The low temperature region gradually expands. This temperature distribution leads to processing spots in the width direction of the fiber sheet traveling in multiple stages up and down.

  An object of the present invention is to achieve a uniform temperature distribution in the sheet width direction in such a heat treatment chamber, and at the same time, a heat treatment furnace for a fiber sheet capable of realizing a reduction in the cost required for it, particularly a precursor fiber in a carbon fiber production process. An object of the present invention is to provide a heat treatment furnace suitable for the flameproofing process.

The inventors have conducted a number of experiments and examinations as to what means should be adopted in order to minimize the facilities arranged in the circulation flow path and at the same time achieve the above object with the minimum necessary facilities. And repeated. The main investigation was made mainly on the basic structure of a convection heating type hot air circulating furnace as a conventional typical fiber sheet heat treatment furnace. In other words, a hot air circulation path is provided in the furnace, a heat treatment chamber is arranged in the circulation path, a heating device is arranged downstream of the circulation flow path of the hot air derivation section of the heat treatment chamber, and hot air is introduced into the heating device and the heat treatment chamber. The convection heating type hot-air circulation furnace in which a circulation fan was arranged in the circulation channel between the two parts was examined.

  The examination item was to elucidate the cause of the temperature difference in the convection heating type hot air circulating furnace based on the verification result of the actual temperature distribution of the processing gas in the heat treatment chamber. Therefore, as a result of repeated experiments, the cause of the temperature difference in the fiber sheet width direction is that the circulation fan has a function of blowing air along the treatment gas circulation flow path as described above, but the treatment gas circulation There is no gas mixing function in the transverse direction of the flow path, and the temperature distribution in the seat width direction differs for each course between the inner and outer circumferences of the gas circulation flow path, and there is almost no change in the temperature distribution even when going round by each course. A temperature difference is generated for each course in the sheet width direction. Also, the cause of the temperature difference in the vertical direction of the fiber sheet traveling in multiple stages up and down is formed between the processing gas directly heated by the heater that becomes the heating surface of the heating device, and the heater mounting frame and the heater This is because there is a processing gas that does not directly heat without touching the heater, and there is no means for mixing these processing gases in the vertical direction.

  Furthermore, as another cause of the temperature difference between the sheet width direction and the processing chamber height direction in the heat treatment chamber, in addition to the above two causes, heat radiation to the floor surface on the gas circulation flow path in the heat treatment chamber. In some cases, the hot gas tends to flow upward. However, regarding the temperature difference between the upper and lower sides, if the temperature difference in the sheet width direction is small, if you look at a series of sheets that run in multiple stages up and down in the heat treatment chamber, as long as you see the temperature distribution for each stage during the heat treatment, There is no significant difference in the processing temperatures for the sheet portions running on the same stage, and the problem remains that it is difficult to obtain the required high temperature.

  The experimental results at this time are shown in FIG. This figure shows the temperature distribution of the gas at the processing gas inlet of the heating device when the processing gas inlet of the rectifying box, which will be described later, is seen from the front, on the downstream side of the circulation fan. In FIG. 8, the dark color portion in the upper left corner of the drawing is the highest temperature, and gradually becomes lighter toward the lower right corner, and becomes lower as this light color progresses. As can be understood from the figure, the inner upper part on the heat treatment chamber side is hot, the temperature decreases as it goes downward, the temperature decreases as it goes from the inner upper part to the outer upper part on the heat treatment chamber side, and the temperature decreases as it goes downward from the outer upper part. The outer bottom corner is the coldest.

The present invention has finally been achieved as a result of such experiments and examinations.
That is, the basic configuration of the present invention is provided with a heat treatment chamber having a hot air introduction portion and a hot air derivation portion in a hot air circulation passage arranged in a horizontal space, and is located outside the heat treatment chamber and is located in the hot air introduction portion. A heat treatment furnace for a continuous fiber sheet in which a processing gas heating device and a circulation fan are arranged in an upstream hot air circulation channel, wherein the fiber sheet is interposed between the hot air introduction unit and the hot air deriving unit. The heat treatment chamber has a fiber travel path that travels horizontally in parallel at least one step up and down, a gas heating region in which the heating device constitutes a processing gas heating surface, a gas heating region and a mounting frame for the gas heating surface, A gas non-heating region is provided between the gas heating region at least between the end of the gas heating region on the floor surface side and the attachment frame, and the flow of the processing gas is directed to the gas heating region. It is that a wind direction control member is arranged.

According to a preferred aspect, the wind direction control member is arranged in a hot air circulation channel adjacent to the gas non-heating region. The wind direction control member is preferably made of a SUS plate, and may be disposed over the entire length in the width direction of the fiber sheet. In addition, the wind direction control member may be installed in a portion that closes the gas non-heated region, and the wind direction control member is installed so that the whole can be tilted and fixed around the floor of the hot air circulation channel. You can also The height of the wind direction control member from the floor surface is preferably 150 to 250 mm.

  Desirably, the hot air introduction part and the hot air outlet part of the heat treatment chamber each have a hot air blowing nozzle and a hot air sucking nozzle, respectively, upstream of the hot air blowing nozzle and downstream of the hot air sucking nozzle. Each adjacent hot air circulation channel has first and second rectification boxes. Furthermore, a 2nd heating apparatus can also be distribute | arranged to the hot air inlet_port | entrance of the rectification | straightening box by the side of the said hot air introduction part.

According to the present invention having the above configuration, the following specific effects are obtained.
(1) Uniformity of temperature distribution When the processing gas passes through the heating device, a gas heating region constituting the processing gas heating surface, and a gas non-heating region between the gas heating region and the mounting frame of the gas heating surface At this time, the processing gas that passes through the gas non-heating region is not heated by the heating device as compared with the processing gas that passes through the gas heating region, and is introduced into the heat treatment chamber while maintaining a low temperature state. Is done. Among the processing gases that pass through these non-heated regions, the processing gas that flows along the floor surface becomes a further low-temperature flow due to the heat dissipation effect on the floor surface, and is introduced into the processing chamber without being mixed. The temperature of the processing gas flowing in the vicinity of the first or second-stage seat travel path (lower path) from the surface to the upper side is lower than that of the upper-stage seat travel path (upper path). This means that in addition to the difference in temperature distribution in the fiber sheet width direction as described above, there is also a difference in the temperature distribution in the vertical direction of the heat treatment chamber.

  On the other hand, according to the present invention, as described above, the flow of the processing gas that passes through the gas non-heating region at least between the gas heating region end on the floor surface side and the mounting frame is transferred to the gas heating region. Therefore, the processing gas passing through the gas non-heating region on the floor side can be flowed toward the gas heating region, forcibly heated, and then introduced into the heat treatment chamber. As a result, the temperature distribution in the width direction of the fiber sheet in the heat treatment chamber can be made uniform in the path worth the height at which the control member is installed, the heat treatment on the fiber sheet is also made uniform, and a uniform and high-quality product can be obtained.

  Since this wind direction control member can be installed close to only a region where temperature drop is a concern, it is possible to finely equalize the temperature distribution corresponding to the specific temperature distribution in the heat treatment chamber. For example, when the heat radiation by the ceiling surface is large and the hot air temperature drop in the upper path is remarkable, it can be dealt with by arranging a wind direction control plate in the non-heating area on the ceiling side. Further, since the cross-sectional area in the circulation flow path by the wind direction control member is at most about 10%, there is little pressure loss, and the wind speed hardly decreases.

(2) Cost advantage Since the wind direction control member is a simple structure like a simple plate, it is easy to manufacture, attach and detach, and the raw material cost, manufacturing cost, installation cost, etc. are extremely low. It becomes.

It is a top view which shows the example of an internal structure of the fiber sheet heat processing furnace of this invention. It is a side view which expands and shows typically the installation part of the wind direction control member in this invention. It is a front view which abbreviate | omits and shows a part which looked at the heating apparatus in this embodiment from the process gas downstream. It is a graph which compares and shows the data of the temperature distribution of the width direction in the sheet | seat travel path of the 1st step | paragraph from the upper end when not installing the wind direction control member. It is a graph which compares and shows the data of the width direction temperature distribution in the sheet | seat driving path of the 2nd step | paragraph similarly from an upper end. It is a graph which compares and shows the data of the temperature distribution of the width direction in the sheet | seat driving path of the 3rd step | paragraph similarly from an upper end. It is a graph which compares and shows the data of the temperature distribution in the width direction in the 4th sheet | seat driving path similarly from an upper end. It is a temperature distribution figure of the up-and-down and right-and-left in the process gas inlet_port | entrance of the rectification | straightening box when not installing a wind direction control member.

Hereinafter, representative embodiments of the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a schematic plan sectional view of the inside of a continuous fiber sheet heat treatment furnace of the present invention as viewed from above, and FIG. 2 is a side view schematically showing an installation portion of a wind direction control member in the present invention. . FIG. 3 is a front view showing a part of the heating device according to the present embodiment as seen from the downstream side of the processing gas. The continuous fiber sheet heat treatment furnace according to this embodiment is exemplified by a flameproofing furnace disposed in the flameproofing process of the carbon fiber manufacturing process, but is not necessarily limited to the flameproofing furnace. In this embodiment, a circulating parallel flow heat treatment furnace is used in which the heat treatment gas flows in parallel to the traveling direction of the continuous fiber sheet that travels in one direction in the heat treatment chamber disposed in a part of the gas circulation flow path. ing.

  As shown in FIG. 1, the continuous fiber sheet heat treatment furnace 10 of the present invention includes a furnace wall 11 having a rectangular frame shape in plan view, and a hot air circulation flow path 12 for process gas is formed using a horizontal space inside the furnace wall 11. Is formed. A heat treatment chamber 13 for heat-treating the continuous fiber sheet TS is disposed in a partial straight region of the hot air circulation channel 12. In the heat treatment chamber 13, there is a sheet processing space 13 a in which the continuous fiber sheet TS travels in multiple stages. In order to run the continuous fiber sheet TS in multiple stages in the vertical direction, a plurality of folding rollers (not shown) extending in the sheet width direction are arranged in the outdoor vertical direction at both ends of the fiber sheet running direction of the heat treatment chamber 13. The continuous fiber sheet TS introduced from the formed fiber sheet supply port travels inside the heat treatment chamber 13 and is folded by a not-shown folding roller disposed at the first-stage fiber sheet outlet. Is reversed by a second-stage folding roller disposed at the fiber sheet outlet formed at the other end of the heat treatment chamber 13 and travels in the reverse direction inside the heat treatment chamber 13. This is repeated for the required number of stages, and when a predetermined heat treatment is performed, the continuous fiber sheet TS is sent out to the next line process. The aforementioned heat treatment is continuously performed by the processing gas heated to a predetermined temperature circulating through the hot air circulation passage 12. According to this embodiment, heated air is used as the processing gas, and the atmospheric temperature in the heat treatment chamber 13 is set to approximately 200 to 300 ° C. Further, the raw fiber of the continuous fiber sheet TS used in the present embodiment is an acrylonitrile-based long fiber that is a typical precursor fiber of carbon fiber. Here, the fiber sheet is a large number of single fibers. A bundle of a plurality of long fiber bundles arranged in parallel to form a single sheet.

  In the heat treatment chamber 13, in addition to the entrance and exit of the continuous fiber sheet TS and a plurality of folding rollers arranged at the sheet entrance and exit, adjacent to the sheet entrance and exit of the heat treatment chamber 13, each hot air circulation channel 12 is provided. The 1st and 2nd rectification | straightening boxes 14 and 15 distribute | arranged along are attached. The first and second rectifying boxes 14 and 15 correspond to the hot air introduction section and the hot air extraction section in the present invention. At each connection portion between the first and second rectifying boxes 14 and 15 and the heat treatment chamber 13, fresh hot air blowing nozzles 16 into the heat treatment chamber 13 and hot air from the heat treatment chamber 13 are circulated. A treated hot air suction nozzle 17 is interposed in the path 12.

  In the hot air circulation flow path 12 excluding the heat treatment chamber, the upstream side of the first rectification box 14 that is the hot air introduction portion of the heat treatment chamber 13 and the downstream side of the second rectification box 15 that is the hot air derivation portion of the heat treatment chamber 13. The heating device 18 and the circulation fan 19 are sequentially installed from the upstream side to the downstream side in the hot air direction on the circulation channel between the two. That is, the treated hot air whose temperature has been lowered after the heat treatment of the continuous fiber sheet TS in the heat treatment chamber 13 is sucked into the second rectifying box 15 through the suction nozzle 17 and is circulated in the middle. After being exchanged for fresh air in the road and exchanging heat, it passes through the heating device 18 and is heated to a required temperature. At this time, the temperature of the hot air in the channel width direction flowing through the circulation channel is lower in the inner hot air than in the outer hot air. Conventionally, the temperature distribution at this time does not change even when flowing inside the heat treatment chamber 13, as shown in FIG.

  By the way, the conventional heating device disposed on the circulation flow path is, as shown in FIG. 2, except for a part, a plurality of coil-made electric heaters (flat heaters) having a flat heating surface. 18a is arranged in multiple stages in the gas flow direction, and these flat heaters 18a have a rectangular frame surrounding the flat heaters 18a arranged in multiple stages with their heating surfaces directed in the hot air flow direction. It is attached to 18b and installed vertically on the floor surface of the circulation channel. When the flat heater 18a is attached to the frame 18b, a frame-like gap is inevitably generated between the flat heater 18a and the frame 18b. Therefore, when hot air passes through the heating device 18, the hot air passing through the upper, lower, left and right ends simply passes through the gap between the flat heater 18a and the frame 18b, and directly contacts the heating surface of the heater. Then, it is sent to the heat treatment chamber 13 by the circulation fan 19 arranged on the downstream side without being heated. At this time, as described above, the temperature distribution of the hot air sent into the heat treatment chamber 13 has almost no fluctuation for each course in the width direction of the circulation flow path, but in the heat treatment chamber 13, the hot air flowing in the vicinity of the floor surface in particular. The temperature is relatively lower than the temperature of the hot air flowing near the ceiling.

  The present invention prevents such fluctuations in the temperature distribution inside the heat treatment chamber 13. Therefore, in the illustrated embodiment, as shown in FIG. 1 to FIG. 3, the wind direction control member 20 constituting the characteristic part of the present invention is formed on the lower end portion of the front surface on the circulating fan 19 side of the heating device 18 as a precursor fiber sheet. It is arranged over the entire width of the. According to this embodiment, a flat SUS plate material is adopted as the wind direction control member 20, and its horizontal width is 1135 mm, which is the dimension between the left and right frame ends of the heating device 18, and the height from the floor surface. The height is set to 250 mm, which is a height that completely covers the nichrome wire heater disposed at the lowermost end of the heating surface.

  Here, these values are not limited, and the height, the arrangement width, and the arrangement position are not limited to the illustrated examples, and can be arbitrarily changed as necessary. Regarding the shape of the wind direction control member 20, in addition to the flat plate shape, the cross section may be a right-angled triangle or a curved surface projecting up and down with the surface facing the hot air. In the present embodiment, no wind direction control member is disposed in the gap between the upper frame portion of the heating device 18 and the flat heater 18a. This is because, when there is a temperature difference between the upper and lower sides as a property of hot air, hot hot air gathers upward, so that there is almost no temperature drop in the temperature of hot air passing through the gap. This is because the same can be said for the gap between the left and right frame portions of the heating device 18 and the flat plate heater 18a, and therefore it is sufficient to arrange the flat plate material.

  Further, in the present embodiment, as indicated by phantom lines in FIG. 1, in order to make the temperature distribution in the sheet width direction more uniform with the hot air introduced into the heat treatment chamber 13, the hot air inlet of the first rectifying box 14 is used. The 2nd heater 21 can also be arrange | positioned before this.

  Hereinafter, the present invention will be described more specifically based on examples and comparative examples.

Example 1
In the heat treatment furnace having the configuration shown in FIGS. 1 and 2, the case where the wind direction control member is installed and the case where the wind direction control member is not installed are not passed through the fiber sheet traveling path of the first to fourth stages (pass). Using four paths formed between the upper and lower sides of the folding roller (not shown), the path width direction temperature at the center in the longitudinal direction of each traveling path in the heat treatment chamber is measured at five points for each path. The temperature distribution in the direction and height direction was investigated. The average temperature in the heat treatment furnace at this time was 240 ° C. The wind direction control member is a rectangular flat SUS plate adjacent to the downstream side of the heating device arranged on the circulation flow path of the heat treatment furnace so as to block the hot air flow area from the floor to a height of 183 mm. Installed perpendicular to the flow direction. The total height of the heating area and the non-heating area in the heating device at this time is 1436 mm.

  While hot air circulates in the heat treatment furnace, the temperature at 5 points in the width direction of each pass is measured at the center in the longitudinal direction of the heat treatment chamber using temperature sensors installed in the furnace. The temperature difference between was recorded. The results are shown in FIG. 4 to FIG. 7, and the temperature difference between both ends, that is, the values obtained by dividing the inner side temperature by the outer side temperature are summarized in Table 1. 4 to 7, the solid line indicates the case where the wind direction control member is installed, the broken line indicates the case where the wind direction control member is not installed, the symbol L indicates the outer course, and R indicates the inner course. As shown in Table 1, the outer direction of the hot air is more relative to the inner direction than the inner direction before and after the installation of the airflow direction control member in the first to fourth pass. The temperature difference is 1.9 ° C, 2.4 ° C, 2.7 ° C, 3.3 ° C in each pass when the airflow direction control member is installed. It can be understood that the temperature difference after installation of the wind direction control member is significantly reduced.

(Example 2)
The experiment was performed under the same conditions as in Example 1 except that the acrylonitrile-based precursor fiber sheet was passed through the circulation flow path in the heat treatment furnace constituted by the four passes. The results are shown in Table 2. As shown in Table 2, the temperature difference in the width direction of each pass was 2.2 ° C., 3.1 ° C., 4.2 ° C., and 3.9 ° C. from the upper stage in the furnace having an average of 240 ° C.

(Comparative Example 1)
During the hot air circulation in the furnace, no wind direction control member is installed on the downstream side of the heating device installed in the circulation flow path in the heat treatment furnace constituted by four passes, and the fiber sheet is not passed through the treatment space of the heat treatment chamber. When the temperature at the five points in the width direction of each pass was measured at the center in the longitudinal direction of the heat treatment chamber, the temperature difference in the width direction of each pass in the furnace at an average of 240 ° C. was 1.7 ° C., 2 ° C. from the top as shown in Table 1. 7 ° C, 6.3 ° C, and 6.3 ° C. As can be understood from this result, in the temperature distribution in the conventional heat treatment chamber, the inner temperature is extremely higher than the outer temperature in the width direction of the circulation flow path, and the temperature difference is large. Also, the temperature in the height direction of the circulation flow path becomes lower as it goes toward the floor surface, particularly in the outer direction, and the temperature difference is large.

(Comparative Example 2)
A PAN precursor is introduced during the hot air circulation in the furnace with nothing installed in the heating unit flow path downstream of the heating device of the circulation flow path in the heat treatment furnace constituted by four passes, and the longitudinal direction of the processing chamber When the temperature at the five points in the width direction of each pass was measured at the center, the temperature difference in the width direction of each pass in the furnace at an average of 240 ° C. was 2.0 ° C., 2.8 ° C. from the upper stage as shown in Table 2. It was 6.6 ° C. and 7.9 ° C. From this result, when the fiber sheet is passed through the temperature distribution in the conventional heat treatment chamber, the inner temperature is relatively higher than the outer temperature in the width direction of the circulation flow path, and the temperature difference is also greater than the fiber sheet. It can be understood that there is a difference even when compared with the case of not passing through.

  In the above examples and comparative examples, the values displayed by the temperature sensor fixedly installed in the furnace in which the temperature measurement has already been described were compared, but each position width in the vicinity of the blowing nozzle and the suction nozzle in the furnace. Similar results were obtained when a thermocouple was installed in the direction and the data obtained from the temperature detector were compared.

  Thus, in order to avoid the hot air flowing along the floor surface downstream of the heating unit from passing through the non-heating area of the heating device and not being directly heated by the heating surface of the superheater, the wind direction control member is installed and the floor surface The wind cooled by heat dissipation was forcibly heated, and the temperature difference in the width direction of the lower pass could be reduced. On the other hand, the temperature difference in the upper path did not change, so the overall temperature distribution could be improved by improving only the hot air temperature distribution in the lower part without affecting the upper streamline behavior. It was.

10 (continuous) fiber sheet heat treatment furnace 11 furnace wall 12 hot air circulation flow path 13 heat treatment chamber 13a sheet treatment space 14 first rectification box 15 second rectification box 16 blowing nozzle 17 suction nozzle 18 heating device 18a heating surface (flat plate shape) heater)
18b Frame 19 Circulating fan 20 Air direction control member (SUS plate)
21 Heater (heating device)

Claims (8)

A heat treatment chamber having a hot air introduction section and a hot air deriving section is provided in a hot air circulation passage arranged in a horizontal space, and a processing gas is provided outside the heat treatment chamber and in the hot air circulation passage upstream of the hot air introduction section. A continuous fiber sheet heat treatment furnace in which a heating device and a circulation fan are sequentially arranged,
The fiber sheet has a fiber travel path that travels horizontally in parallel at least one step up and down in the heat treatment chamber between the hot air introduction section and the hot air extraction section,
The heating device has a gas heating region constituting a processing gas heating surface, and a gas non-heating region between the gas heating region and a mounting frame of the gas heating surface,
At least a wind direction control member that directs the flow of the processing gas that passes through the gas non-heating region between the gas heating region end on the floor surface side and the mounting frame of the gas heating surface to the gas heating region is disposed. Heat treatment furnace for fiber sheets.   The heat treatment furnace according to claim 1, wherein the wind direction control member is disposed in a hot air circulation channel adjacent to the gas non-heating region.   The heat treatment furnace according to claim 1 or 2, wherein the wind direction control member is made of a SUS plate and is disposed over the entire length in the width direction of the fiber sheet.   The heat treatment furnace according to any one of claims 1 to 3, wherein the wind direction control member is installed at a portion that closes the gas non-heating region.   The heat treatment furnace according to any one of claims 1 to 3, wherein the wind direction control member is installed so as to be tiltable and fixable around the floor surface of the hot air circulation channel.   The heat processing furnace in any one of Claims 1-5 whose height from the floor surface of the said wind direction control member is 150-250 mm.   The heat treatment furnace according to claim 1, wherein the hot air introduction part and the hot air lead-out part of the heat treatment chamber each have a hot air blowing nozzle and a hot air sucking nozzle.   The heat treatment furnace according to claim 1, wherein a heating device is arranged at a hot air inlet of the rectifying box.