JPS6030762B2 - Hot air heating furnace for carbon fiber production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot-air heating furnace for producing carbon fibers that uniformly heats multiple threads running in parallel.

When heating a fibrous material to give it physical or chemical modification, there is a method of heat treatment by contacting the fibrous material with hot air.In particular, polyacrylonitrile, pitch,
In the flame-retardant process during the production of carbon fibers using polyvinyl alcohol as a precursor, it is common to use a heating furnace that brings hot air into contact with the fibrous materials when heat-treating them under temperature and atmospheric conditions. It is. The temperature history during this heat treatment process greatly affects quality.

For this reason, in the so-called multi-filament simultaneous processing method in which the fibrous material is run in parallel as multiple filaments, it is necessary that there is virtually no difference in the temperature history between each thread. It is required that there be substantially no temperature variation between each yarn over the entire inner area. Therefore, in the hot air heating furnace, uniformity of air velocity is extremely important in order to maintain temperature uniformity within the furnace.

However, it is actually difficult to equalize the wind speed applied to each yarn in a hot air heating furnace. For example, a hot air heating furnace used in the process of making the precursor fiber flame resistant;
In other words, in order to circulate hot air within the furnace, a flameproofing furnace connects a hot air blowing part and a hot air suction part provided at the end of the furnace through a duct with a circulation fan and a heater interposed outside the furnace. It's normal. However, the hot air from the hot air blowing section tends to be affected by the shape of the hot air blowing surface in particular, resulting in turbulent airflow and non-uniform wind speed among the yarns.

As a result, the temperature inside the furnace becomes non-uniform among the yarn groups, increasing the variation in quality, and on the other hand, yarn entanglement, yarn breakage, roller winding, etc. due to uneven wind speed are likely to occur. In some cases, this may cause the so-called '1 burn phenomenon' in which the yarn to be treated suddenly burns in the furnace, which is a particular problem in the production of carbon fibers. By solving the technical problems, uniformizing the speed of hot air blown onto each yarn running in parallel in the heating furnace, and reducing temperature variations in the furnace, we have improved the quality of carbon fiber. It is an object of the present invention to provide a hot air heating furnace that can prevent operational troubles.

The configuration of the present invention that achieves this object is that in a hot air heating furnace for manufacturing carbon fibers that processes multi-filament threads running in parallel, a hot air blowing surface for blowing hot air along the surface of the running thread group is provided. , a hot air blowing section comprising a direction changing guide vane for directing the hot air to the hot air blowing surface, and a rectifying perforated plate or wire mesh with a porosity of 30 to 50% on one or both of the front and rear sides thereof. The hot air supplied from the hot air circulation duct outside the furnace is directed from the hot air blowing surface into the furnace through the direction changing guide vane in the hot air blowing section and one or both of the front and rear rectifying perforated plates or wire meshes. It is characterized by blowing out air. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hot air heating furnace for producing carbon fibers according to the present invention, particularly a flameproofing furnace for firing polyacrylonitrile, will be specifically described with reference to the drawings.

FIG. 1 is a schematic front sectional view of a flameproofing furnace for producing carbon fibers, which is an embodiment of the present invention, and FIG. 2 is a schematic side view of FIG. 1.

In the figure, the thread 2 is a plurality of pairs of guide rollers 3a, 3b, . . . 3 provided below and above the heat treatment chamber 1.
The yarn 2 is sequentially transferred to the storage section e, during which the yarn 2 is heat-treated.

The heat treatment chamber 1 has a hot air blowing section 4 at the bottom thereof with a blowing surface 4'.
are provided so as to face the upper rollers 3b and 3d, and hot air is blown out from the blowing surface 4' along the yarn 1 surface. The hot air in the room is removed from the hot air suction unit 5 (
5': discharged through the suction bow l surface). The hot air blowing part 4 and the hot air suction part 5 are of the outside-furnace roller type (a guide roller is provided outside the furnace) flameproofing furnace.
The number of hot air blowing units 4 is provided in accordance with the number of times the yarn 2 enters and exits the heat treatment chamber 1, and in particular, in this embodiment, the hot air blowing unit 4 is provided at the bottom of the heat treatment chamber 1, and the hot air suction unit 5 is provided at the top of the heat treatment chamber 1. The flow of hot air in the heat treatment chamber 1 is almost parallel to the yarn group surface of the yarn 2 from bottom to top.

In addition, the duct 6 that supplies hot air to the hot air blowing unit 4 is connected to a duct 7 that discharges hot air from the hot air suction unit 5, and a fan 9 that is provided outside to circulate the hot air and a heater 8 that heats the hot air to a predetermined temperature. connected via. The feature of the present invention lies in the structure of the hot air blowing section 4.

That is, as shown in FIG. 3, in the hot air blowing section 4, the hot air from the hot air circulation duct 6 is first rectified by a perforated plate 10 (corresponding to a hot air supply port) such as a punched metal. The perforated plate 10 here should have a porosity of 30 to 50% in order to have a rectifying function, so the pore diameter should be about 3 to 8 inches, and the holes should be made relative to the plate. Preferably one that is evenly spaced.

At this time, if the porosity is less than 30%, although the rectification effect will be enhanced, the pressure loss of the hot air will increase, leading to an increase in operating costs.

On the other hand, if it exceeds 50%, the hot air rectification effect becomes insufficient, leading to operational troubles such as entanglement of the yarn to be treated due to uneven wind speed and yarn breakage due to yarn sway. Become. In addition, here, a perforated plate 1 is used for rectifying hot air.
0 is shown, but in addition to this, it may be replaced directly with a rectifying wire mesh having a desired rectifying effect on hot air.

However, similarly to the perforated plate 10, the porosity of the wire mesh for flow straightening should be maintained within the range of 30 to 50%. perforated plate 10
'Thus, the rectified hot air is
The direction is changed to a substantially right angle direction by a direction changing guide vane 13 provided inside. A plurality of guide vanes 13 are provided at positions where it is desired to change the direction of the hot air from the duct 6.

Further, the guide vanes 13 are arranged in gradual steps such that the guide vanes are at the top at the position closest to the duct and at the bottom at the farthest position so that the direction of the hot air is changed over the entire width of the yarn. However, the arrangement can be done in the opposite way.

Further, it is preferable that the guide blade 13 has a width close to the inside of the hot air blowing part 4. Normally, the guide vanes 13 have a quarter-arc shape, for example, and are arranged at approximately equal intervals, but the shape, arrangement interval, etc. are not particularly limited.

However, if the guide blade 13 is structured so that its direction can be changed freely, it is convenient to adjust the wind speed in the heat treatment chamber 1 as desired from the viewpoint of the quality of the yarn 2. The hot air converted in the right angle direction by the guide vanes 13 is further directed to the heat treatment chamber 1 from the hot air blowing surface 4r having a rectifying function, which is made up of a perforated plate 10' (a rectifying wire mesh may also be used) provided behind the guide vanes 13. In addition, the yarn is blown out along the yarn group surface, and the yarn to be treated is heat-treated. Next, another embodiment of the thermal storm outlet according to the present invention will be described.

That is, the hot air blowing section shown in FIG. 4 has perforated plates 10, 10' and rectifying wire meshes 11, 11' attached before and after the direction changing guide vane 13.

The hot air blowing section 4 shown in FIG. 5 has a structure that can be applied only to the end of the flameproofing furnace shown in FIG. There is. Of course, these functions are exactly the same as the hot air blowing section shown in FIG. In addition, in the present invention, if the hot air suction part 5 is also provided with a guide vane for direction change and a perforated plate in the same way as the blowing part 4, the effect will be further increased, but the effect of the present invention is mainly due to the structure of the blowing part. satisfied by.

Although not shown, there is also a yarn 2 inside the heat treatment chamber 1.
It is also possible to further increase the effect of uniform wind speed by providing a rectifying wire mesh or the like that does not impede the running of the vehicle. As mentioned above,
As a hot air blowing part in a hot air heating furnace for producing carbon fibers, a direction changing guide vane 13, a perforated plate 10 in front and behind the direction changing guide vane 13,
10' (and/or rectifying wire mesh), the uniformity of the wind speed inside the furnace is much better than before. For example, when the average wind speed inside the furnace is 2 m/sec,
It became possible to easily adjust the variation within 1.5 to 2.5 m/sec.

This drastic reduction in wind speed variation has a corresponding reduction in temperature variation in the furnace, which not only greatly improves the quality variation of heat-treated yarns, but also improves the quality of yarns caused by wind speed unevenness. Entanglement, yarn breakage, roller wrapping, etc. are significantly reduced, and the "burn phenomenon" of treated yarns, which is a particular problem in carbon fiber production, can be completely prevented, which is an extremely remarkable effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic front sectional view of a flameproofing furnace for producing carbon fibers showing one embodiment of the present invention, and FIG. 2 is a schematic side view of the flameproofing furnace in FIG. 1. Further, FIGS. 3 and 4 are sketches of the hot air blowing section, and FIG. 5 is a sketch of the vicinity of the end of the flame-resistant furnace in FIG. 1. 1: Heat treatment chamber, 2: Yarn, 3a to 3e: Guide roller,
4: Hot air blowing section, 5: Hot air suction section, 6, 7: Hot air circulation duct, 8: Heater, 9: Fan, 10, 10': Perforated plate, 11, 11' Wire mesh, 12: Inside of hot air blowing section Space, 13: Guide vane. Figure 2 Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A hot air blowing surface for blowing out hot air along the surface of a group of running yarns in a hot air heating furnace for producing carbon fibers that processes multi-filaments running in parallel; The furnace is equipped with a hot air blowing section that has direction changing guide vanes for directing the hot air toward the exit surface, and a rectifying perforated plate or wire mesh with a porosity of 30 to 50% on either or both of the front and rear sides. The hot air supplied from the outside hot air circulation duct is blown into the furnace from the hot air blowing surface through the direction changing guide vane in the hot air blowing part and one or both of the front and rear rectifying perforated plates or wire meshes. A hot air heating furnace for producing carbon fiber. 2. The hot-air heating furnace for producing carbon fibers according to claim 1, wherein the direction-changing guide vanes are direction-changeable. 3
The hot air heating furnace for producing carbon fibers according to claim 1, wherein the hot air heating furnace for producing carbon fibers is a flame-retardant furnace.