JP2003183975A - Heat treating oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treating oven which can prevent hot gas from flowing out a heat treating chamber and prevent outer gas from flowing in the chamber without setting additional equipment and has excellent temperature uniformity in the chamber, and to provide a method for producing carbon fibers with the heat treating oven. <P>SOLUTION: This heat treating oven has a heat treating chamber, a hot gas exhaust port and a hot gas supply port disposed on the upper and lower sides of the chamber, respectively. A yarn-feeding and yarn-drawing ports are disposed on the sides of the chamber, and fibers travel in the horizontal direction. Simultaneously blowing hot gas is blown on the lower sides of the fibers. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment furnace suitable for producing carbon fibers and a method for producing carbon fibers using the furnace.

[0002]

2. Description of the Related Art A conventional heat treatment furnace, particularly a heat treatment furnace used for producing carbon fibers, includes a hot air supply port provided on the upper surface of the heat treatment chamber and a hot air discharge port provided on the lower surface thereof, and a yarn on the side wall of the heat treatment chamber. There is known a heat treatment furnace that has an inlet and a yarn outlet, and that heats the yarn by blowing hot air from above onto the yarn while horizontally moving the yarn in the heat treatment chamber (for example, See Patent Document 1).

In such a heat treatment furnace, for example, when it is a flameproofing furnace, a yarn made of a plurality of polyacrylonitrile (PAN) type precursors (precursor fibers) has an arbitrary pitch in a horizontal plane. While being maintained, it is introduced into the heat treatment chamber, and the guide rollers installed on both sides of the heat treatment chamber repeat the movement in and out of the heat treatment chamber while reversing the traveling direction, traveling while maintaining an arbitrary pitch in the vertical direction of the heat treatment chamber, Flameproofed.

In the heat treatment furnace disclosed in Patent Document 1, a seal chamber is provided adjacent to the outside of the yarn introduction port and the yarn discharge port on the side wall of the heat treatment chamber, and the exhaust chamber is provided in the seal chamber. The hot air flowing out of the heat treatment chamber is exhausted to prevent the harmful gas from leaking out of the furnace, and the outside air is prevented from flowing into the heat treatment chamber.

[0005]

[Patent Document 1] Japanese Patent Application Laid-Open No. 11-173761 (second
(See page 6, Fig. 1)

[0006]

However, in the heat treatment furnace disclosed in the above-mentioned Patent Document 1, as one means for increasing productivity, when the number of yarn steps entering and leaving the heat treatment chamber is increased, the flow is The resistance that occurs when passing through the pipe increases, and the pressure drop that occurs from upstream to downstream of the flow increases. For this reason, the pressure difference between the heat treatment chamber and the atmosphere outside the furnace also increases, and it becomes impossible to prevent the outside air from flowing into the heat treatment chamber only with the seal chamber. As a result, the hot air in the heat treatment chamber flows out from the yarn introduction port and the yarn discharge port provided above the heat treatment chamber, and the outside air is discharged from the yarn introduction port and the yarn discharge port provided below the heat treatment chamber into the heat treatment chamber. To flow into.

There is a problem that the inflow of outside air into the heat treatment chamber causes temperature unevenness in the heat treatment chamber and deteriorates product quality. Further, in the region where the outside air flows, the heat treatment of the yarn does not proceed because the temperature is low, and the productivity is reduced. Further, when the hot air discharged from the hot air outlet is returned to the hot air supply port for circulation, the circulating hot air whose temperature has been lowered by the inflow of outside air increases the power consumption of the heater for heating it again to the desired temperature. However, there is a problem that energy efficiency decreases.

In addition, in the above heat treatment furnace, in order to exhaust hot air flowing out from the heat treatment chamber and suppress the inflow of outside air into the heat treatment chamber, an additional facility called a seal chamber is required outside the heat treatment chamber. There is a problem that the space becomes large, the equipment cost increases, and the manufacturing cost increases.

The object of the present invention is to pay attention to the above problems and prevent hot air outflow to the outside of the heat treatment chamber and inflow of outside air into the heat treatment chamber without installing special additional equipment, and to prevent the temperature inside the heat treatment chamber from increasing. It is intended to provide a heat treatment furnace excellent in uniformity and a method for producing carbon fiber using the heat treatment furnace.

[0010]

The present inventors have found that the above problems can be solved by utilizing buoyancy acting on hot air. That is, according to the present invention, the heat treatment chamber, the hot air discharge port provided on the upper side of the heat treatment chamber and the hot air supply port provided on the lower side, the yarn introduction port and the yarn provided on the side of the heat treatment chamber. Provided is a heat treatment furnace which has a yarn outlet and is adapted to perform a heat treatment by blowing hot air from below onto the yarn while running the yarn horizontally in the heat treatment chamber.

Here, the horizontal direction is a direction substantially parallel to the ground. One of the reasons for making them substantially parallel is that the yarn is suspended by its own weight, and the traveling direction thereof is not completely parallel to the ground. Another reason is that the guide rollers that support the yarns on both sides of the heat treatment chamber have steps, so that even if the traveling direction of the yarns is inclined with respect to the ground, the yarns are on two opposite sides of the heat treatment chamber. This is because the principle of the present invention described below is substantially established if it is passed.

Generally, since the hot air in the heat treatment chamber has a smaller gas density than the outside air, buoyancy acts on the hot air and a pressure gradient occurs in the vertical direction of the heat treatment chamber. That is, the pressure above the heat treatment chamber becomes higher and the pressure below the heat treatment chamber becomes smaller than the pressure of the atmosphere outside the furnace. On the other hand, in the hot air in the heat treatment chamber, a pressure loss occurs due to the resistance when the flow passes through the yarn, and the pressure decreases from upstream to downstream of the hot air.

In the heat treatment furnace of the present invention, the hot air supply port upstream of the hot air is provided on the lower side of the heat treatment chamber, and the hot air discharge port downstream of the hot air is provided on the upper side of the heat treatment chamber so that the flow of the yarn is increased. The pressure gradient generated by the resistance when passing through is set to have the opposite sign to the pressure gradient generated by the action of buoyancy. Therefore, the pressure gradient generated by the action of buoyancy cancels out the pressure gradient generated by the resistance when the flow passes through the yarn, and the pressure gradient generated in the vertical direction of the heat treatment chamber becomes small. As a result, the pressure difference between the heat treatment chamber and the atmosphere outside the furnace becomes small, and hot air outflow to the outside of the heat treatment chamber and outside air inflow to the heat treatment chamber can be prevented without installing any special additional equipment, and the temperature inside the heat treatment chamber can be made uniform. A heat treatment furnace having excellent properties is provided.

In the heat treatment furnace, a plurality of yarns are
In the case of introducing into the heat treatment chamber so as to keep an arbitrary pitch Ph in the horizontal plane and keeping the arbitrary pitch Pv in the vertical direction of the heat treatment chamber while repeatedly moving in and out of the heat treatment chamber, a large amount of yarns can be processed. A possible multi-stage heat treatment furnace is provided.

In a preferred embodiment of the multi-stage heat treatment furnace, the pressure drop amount when hot air passes through the yarn is ΔP.
(Unit: Pa), the buoyancy generated in the hot air based on the difference between the density of the atmosphere outside the furnace and the density of the hot air is F (unit: N / m3),
When the vertical thread pitch is Pv (unit: m),
The temperature is adjusted by adjusting at least one condition selected from the flow velocity of hot air, the temperature of hot air, and the pitches Ph and Pv of the yarns so that F × Pv / ΔP falls within the range of 0.7 to 1.6. A heat treatment furnace having excellent uniformity is provided. F × P
The range of v / ΔP is adopted as a range for preventing outside air inflow.

The reason why the flow velocity of the hot air, the temperature of the hot air, and the pitch Ph of the yarn are used to adjust F × Pv / ΔP will be described below.

ΔP is the amount of pressure drop per stage of yarn that occurs when the flow passes through the yarn. ΔP changes depending on the yarn pitch Ph in the horizontal plane, the yarn shape, the flow velocity of hot air, and the like. Among these, the production conditions that can be changed are the yarn pitch Ph and the flow velocity of the hot air. The value of ΔP may be experimentally measured, may be measured in a production machine, or may be obtained by numerical simulation.

As for the buoyancy F acting on the hot air, the density of the atmosphere outside the furnace is ρ0 (unit: kg / m3), and the density of the hot air is ρ.
If h (unit: kg / m3) and the magnitude of gravitational acceleration are g (unit: m / s2), then F = g (ρ0−ρh). In the case of a heat treatment furnace placed on the ground at room temperature and atmospheric pressure, the magnitude g of gravitational acceleration and the outside atmosphere density ρ0 are almost fixed, so the production conditions that can be changed are the density ρh determined by the temperature of hot air. is there. When the yarns are arranged in multiple stages while maintaining the pitch Pv in the vertical direction of the heat treatment chamber,
The amount of pressure increase per one stage of yarn due to buoyancy is F × Pv.

For the above reasons, F × Pv / ΔP can be obtained by adjusting the flow velocity of hot air, the temperature of hot air, and the pitch Ph of the yarn.
Will be decided.

As another preferred mode of the multi-stage heat treatment furnace, the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P2 in the lower part of the heat treatment chamber is -9 Pa≤P1-P2≤6 Pa.
By adjusting at least one condition selected from the flow velocity of hot air, the temperature of hot air, and the pitches Ph and Pv of the yarns, a heat treatment furnace excellent in temperature uniformity is provided. The range of P1-P2 is adopted as a range for preventing outside air inflow.

The upper part of the heat treatment chamber when measuring the pressure is a region above the uppermost stage of the yarn and below the upper face of the heat treatment chamber. Similarly, the lower part of the heat treatment chamber is a region below the lowermost stage of the yarn and above the lower surface of the heat treatment chamber. The pressures P1 and P2 are static pressures in each region. P1
The pressure difference between P2 and P2 may be obtained as the difference between the pressures in the respective areas measured by an absolute pressure gauge, or the pressure difference between the two areas may be directly measured using a differential pressure gauge. Alternatively, it may be obtained by numerical simulation. Since the measured value fluctuates with time, it is preferable to sample three or more times at each measuring point and use it as the average value. The number of measurement points may be one in each area, or may be measured at a plurality of points in each area and obtained as an average value.

As another preferable mode of the multi-stage heat treatment furnace, if the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P2 in the lower part of the heat treatment chamber is P1-P2> 6 Pa, the flow velocity of hot air becomes large. Adjust, P1-P2 <-
A heat treatment furnace having means for adjusting the flow rate of hot air to be low at 9 Pa is provided.

As means for adjusting the flow velocity of the hot air, there are means for changing the rotation speed of the fan and means for changing the opening degree of the damper. In order to automate this, a detection device for sequentially detecting the pressure difference, and a control device for adjusting the rotation speed of the fan and the opening degree of the damper based on the signal detected by the detection device may be provided. is there.

As another preferable mode of the multi-stage heat treatment furnace, if the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P0 of the atmosphere outside the furnace is P1-P0> 3 Pa, the flow velocity of hot air is increased. Adjust, P1-P0 <-5
If it is Pa, a heat treatment furnace having means for adjusting the flow velocity of hot air to be small is provided.

As another preferred mode of the multi-stage heat treatment furnace, if the relationship between the pressure P2 in the lower part of the heat treatment chamber and the pressure P0 of the atmosphere outside the furnace is P2-P0 <-3 Pa, the flow velocity of hot air is increased. Adjust to P2-P0> 4
If it is Pa, a heat treatment furnace having means for adjusting the flow velocity of hot air to be small is provided. P1-P0 and P
The range of 2-P0 is adopted as a range for preventing outside air inflow.

As another preferred mode of the multi-stage heat treatment furnace, when hot air outflow to the outside of the heat treatment chamber from the yarn introduction port or yarn discharge port in the upper half of the heat treatment chamber is observed, the flow velocity of the hot air is It has a means to adjust so that the flow velocity of the hot air becomes smaller when hot air outflow from the yarn inlet or yarn outlet in the lower half of the heat treatment chamber to the outside of the heat treatment chamber is observed. A heat treatment furnace is provided.

The upper half of the heat treatment chamber is at least a part of the region above the center in the height direction of the heat treatment chamber. Similarly, the lower half of the heat treatment chamber is at least a part of the region below the center in the height direction of the heat treatment chamber.

As another preferred embodiment of the multi-stage heat treatment furnace, there is provided a heat treatment furnace having means for adjusting the flow velocity of the hot air so that the temperature of the hot air discharged from the hot air outlet is maximized.

Further, as another preferable mode in all the heat treatment furnaces, at least one partition plate installed in the horizontal direction is provided in the vertical direction in the untreated zone between the yarn and the side wall constituting the side surface of the heat treatment chamber. A heat treatment furnace having the above is provided.

Here, the untreated zone is a space between the yarn and the side wall forming the side surface of the heat treatment chamber. Specifically, it is a space between a yarn and a side wall that does not have a yarn introduction port or a yarn ejection port among the side walls forming the side surface of the heat treatment chamber. The untreated zone is usually provided in order to prevent the temperature near the side wall from decreasing due to heat dissipation to the outside of the furnace, and to avoid insufficient heat treatment of the yarn. When heat treatment is performed by blowing hot air from below onto the yarn, the hot air from below passes through the untreated zone while avoiding the traveling yarn, so that the untreated zone is blocked by a partition plate for efficient heat treatment. It is possible.

It is more preferable that the partition plate is installed at the same height as the yarn in the vertical direction. Further, it is more preferable that the partition plate is installed from the yarn introduction port to the yarn ejection port in the yarn traveling direction.

Further, all of the above heat treatment furnaces are suitable for use in the production of carbon fiber, can be used as a flameproofing furnace or a carbonizing furnace, and are particularly suitable as a flameproofing furnace.

Therefore, the method for producing carbon fiber according to the present invention comprises a method characterized in that the carbon fiber is produced by using the above-mentioned flameproofing furnace.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example in which the heat treatment furnace of the present invention is used as a flameproofing furnace for carbon fiber production. In the heat treatment chamber 1 in the flameproofing furnace, the hot air discharge port 2 provided on the upper side of the heat treatment chamber and the hot air supply port 3 provided on the lower side of the heat treatment chamber sandwich the yarn 6. Are arranged so as to face each other. On the side wall on the side of the heat treatment chamber 1, the yarn introduction port 4
And the yarn outlet port 5, the yarn 6 runs in the heat treatment chamber 1 in the horizontal direction, and the yarn 6 extends from 200 to 35 from below.
A flameproof treatment is performed by blowing hot air of 0 ° C. Thread introduction port 4
In order to enhance the effect of preventing hot air outflow to the outside of the heat treatment chamber and outside air inflow to the heat treatment chamber, it is preferable that the yarn outlet port 5 has a small opening area to the extent that the yarns do not contact.

The yarn 6 is guided by the guide rollers 7 while reversing the traveling direction, and the yarn introducing port 4 provided on the side wall of the heat treatment chamber 1 is used.
And the yarn outlet 5, and passes through the heat treatment chamber 1 a plurality of times. The yarn 6 runs in the vertical direction of the heat treatment chamber 1 while maintaining an arbitrary pitch Pv determined by the installation interval of the guide rollers 7.

FIG. 2 is an example of the vertical cross section of FIG. A plurality of yarns 6 are introduced while maintaining an arbitrary pitch Ph in the horizontal plane. Among the side walls forming the side surface of the heat treatment chamber, an untreated zone 10 is provided between the side wall having no yarn introduction port or yarn ejection port and the yarn. FIG. 3 is an example of a cross section of a guide roller having a groove. The pitch Ph in the horizontal plane is determined by the pitch of the grooves carved in the guide roller.

FIG. 4 shows an example of the case where the hot air discharged from the hot air outlet 2 is returned to the hot air supply port 3 and is circulated and used. The fan 8 sends the hot air to the hot air supply port 3 and sucks the hot air from the hot air discharge port 2, and the heater 9 controls the hot air to a desired temperature.

As disclosed in Japanese Patent Laid-Open No. 11-173761, a seal chamber may be provided outside the yarn introducing port 4 and the yarn extracting port 5 provided on the side wall of the heat treatment chamber 1.

Hereinafter, the present invention will be described more specifically with reference to Examples.

[0040]

[Example] [Example 1] PA with a thickness of 1.1 decitex
A yarn obtained by bundling 12,000 N-type precursor single yarns was subjected to flameproofing treatment. By providing a hot air supply port on the lower surface of the heat treatment chamber and providing a hot air discharge port on the upper surface, the hot air flowed from the bottom to the top of the heat treatment chamber, and the hot air was blown onto the yarn from below.
The hot air discharged from the hot air outlet was returned to the hot air supply port and used again. The rotation speed of the fan provided between the hot air outlet and the hot air outlet was changed so that the average speed of the hot air at the hot air inlet and the hot air outlet was 1 m / sec. Further, the average temperature of the hot air at the hot air supply port is set to 2 by the heater provided between the hot air discharge port and the hot air supply port.
The temperature was controlled to 50 ° C. The yarn was made to repeat in and out of the heat treatment chamber 19 times while reversing the running direction by guide rollers installed on both sides of the heat treatment chamber. The running speed of the yarn was 0.05 m / sec. The yarn pitch Pv in the vertical direction is 0.2 m, and the yarn pitch P in the horizontal plane
h was 0.01 m. Among the side walls forming the side surface of the heat treatment chamber, a region from the side wall having no yarn introduction port or yarn ejection port to the inside 0.3 m was defined as an untreated zone. The temperature of the atmosphere outside the furnace was 30 ° C.

Thermocouples were arranged at five locations in the height direction of the heat treatment chamber at a position 0.2 m away from the side wall of the heat treatment chamber having the yarn introduction port and the yarn ejection port, and the temperature inside the heat treatment chamber was measured. . The five measurement points are the point A provided near the top of the yarn and the point E provided near the bottom of the yarn.
The remaining three points were provided at approximately equal intervals between points A and E, and were set as points B, C, and D from the top. As a result of the measurement,
A point: 249 ° C, B point: 248 ° C, C point: 247 ° C, D
Point: 249 ° C., E point, 250 ° C., and the difference from the set temperature (average temperature of hot air supply port 250 ° C.) was 3 ° C. at maximum.

Further, a windsock made by cutting a nylon yarn of 78 decitex 24 filaments to a length of about 0.07 m was installed around the yarn inlet and the yarn outlet, and the hot air outflow to the outside of the heat treatment room was observed. The windsock was in a hanging state, and no significant hot air outflow was observed.

[Comparative Example 1] P having a thickness of 1.1 decitex
A yarn obtained by bundling 12,000 AN-based precursor single yarns was subjected to flame resistance treatment. Similar to the conventional heat treatment furnace, the hot air supply port is provided on the upper surface of the heat treatment chamber and the hot air discharge port is provided on the lower surface so that the hot air flows from the top to the bottom of the heat treatment chamber, and the hot air is blown from above the yarn. It was The other conditions were the same as in Example 1. A schematic diagram is shown in FIG.

As in Example 1, the temperature inside the heat treatment chamber was measured. As a result, point A: 249 ° C., point B: 241 ° C., point C:
233 ° C., D point: 170 ° C., E point, 136 ° C., and the maximum difference from the set temperature (average temperature of hot air supply port 250 ° C.) was 114 ° C. From this, it was clear that outside air was flowing in from the yarn inlet and the yarn outlet under the heat treatment chamber.

Further, as in Example 1, a windsock made by cutting a nylon yarn of 78 decitex 24 filaments to a length of about 0.07 m was installed around the yarn introduction port and the yarn ejection port. At the upper part, the windsock fluttered outside the furnace, and a remarkable outflow of hot air was observed. In addition, in the lower part of the heat treatment chamber, the windsock fluttered inside the furnace, and a remarkable inflow of hot air was observed.

As described above, according to the present invention, by flowing hot air from the bottom to the top of the heat treatment chamber, the outflow of hot air from the heat treatment chamber and the inflow of outside air into the heat treatment chamber are prevented, and the temperature uniformity in the heat treatment chamber is improved. I was able to improve significantly.

[Examples 2 to 10] A yarn obtained by bundling 12,000 PAN-based precursor single yarns having a thickness of 1.1 decitex was subjected to flameproofing treatment. By providing a hot air supply port on the lower surface of the heat treatment chamber and providing a hot air discharge port on the upper surface, the hot air flowed from the bottom to the top of the heat treatment chamber, and the hot air was blown onto the yarn from below. The hot air discharged from the hot air outlet was returned to the hot air supply port and used again. By adjusting the rotation speed of a fan provided between the hot air outlet and the hot air supply port, the average velocity of the hot air at the hot air supply port and the hot air discharge port is 0.1 m / sec from 0.6 m / sec to 1.4 m / sec. It changed every second. The other conditions were the same as in Example 1.

In the above heat treatment furnace, a pressure measuring tube was provided on the side wall of the heat treatment chamber at a position 0.1 m away from the uppermost stage of the yarn, and the pressure at this position was P1. By connecting one end of the differential pressure gauge to the pressure measuring pipe and installing the other end outside the heat treatment chamber, the pressure difference between the upper portion of the heat treatment chamber and the atmosphere outside the furnace P1-P0
Was measured. Similarly, 0.1m from the bottom of the yarn to the bottom
A pressure measuring tube was provided on the side wall of the heat treatment chamber at a distant position, and the pressure difference P2-P0 between the lower portion of the heat treatment chamber and the atmosphere outside the furnace was measured. In addition, the pressure difference P1 between the upper part of the heat treatment chamber and the lower part of the heat treatment chamber
-P2 was obtained as the difference between P1-P0 and P2-P0 described above. In addition, as in Example 1, the temperature inside the heat treatment chamber was measured at five points A to E. In the same manner as in Example 1, a nylon yarn of 78 decitex 24 filaments was wound around the yarn introduction port and the yarn ejection port to a length of about 0.07 m.
A cut windsock was installed in the room, and hot air outflow to the outside of the heat treatment room was observed.

The measurement results are shown in Table 1. The pressure range where hot air does not flow out of the heat treatment chamber is −9 Pa ≦ P1−P2
≤6 Pa, -5 Pa ≤P1-P0 ≤3 Pa, -3 Pa≤
It was P2-P0 <= 4Pa.

A method of deriving F × Pv / ΔP shown in Table 1 will be described below. The amount of pressure drop per stage of the yarn generated when the hot air passes through the yarn was obtained by numerical simulation. Specifically, in the two-dimensional cross-sectional model as shown in FIG. 6, the yarn is made solid and the flow velocity of the hot air passing therethrough is changed, so that the pressure drop amount at each flow velocity can be known. As a result of the numerical simulation, the pressure drop amount (unit: Pa) under the above flameproof treatment condition
Was ΔP = 0.93 × U2. Here, U is an average flow velocity of hot air (unit: m / s). Next, the buoyancy F is
If the density of the atmosphere outside the furnace is ρ0 (unit: kg / m3), the density of hot air is ρh (unit: kg / m3), and the magnitude of gravity acceleration is g (unit: m / s2), then F = g (ρ0 −ρ
h) and F = 9.8 × (1.15-0.67) =
It becomes 4.7 N / m3.

The pressure gradient in the heat treatment chamber mainly occurs as a result of the pressure gradient generated by the buoyancy of the hot air and the pressure gradient generated by the resistance when the hot air passes through the yarn, canceling each other out. Therefore, the pressure difference between the upper portion of the heat treatment chamber and the lower portion of the heat treatment chamber becomes smaller as F × Pv / ΔP becomes closer to 1. As shown in Table 1, F × Pv / ΔP is 0.7 to
Within the range of 1.6, hot air did not flow out of the heat treatment chamber. Also, the closer F × Pv / ΔP is to 1, the higher the circulating exhaust gas temperature measured at the hot air outlet. Also, A
The difference between the temperature in the heat treatment chamber measured at 5 points from point E to the set temperature (average temperature of hot air supply port 250 ° C.) is F ×
The smaller Pv / ΔP is closer to 1, the smaller the value.

As described above, according to the present invention, F × Pv /
By adjusting at least one condition selected from the flow velocity U of hot air, the temperature of hot air, and the pitches Ph and Pv of the yarns so that ΔP falls within the range of 0.7 to 1.6, Hot air outflow can be prevented. Also, by adjusting the flow velocity of the hot air so that the temperature of the hot air discharged from the hot air outlet is maximized, the energy consumption of the heater required to circulate the hot air is reduced and at the same time the temperature inside the heat treatment chamber is made uniform. The property is improved.

[0053]

[Table 1]

[Example 11] A yarn obtained by bundling 12,000 PAN-based precursor single yarns having a thickness of 1.1 decitex was subjected to flame resistance treatment. By providing a hot air supply port on the lower surface of the heat treatment chamber and providing a hot air discharge port on the upper surface, the hot air flowed from the bottom to the top of the heat treatment chamber, and the hot air was blown onto the yarn from below. The hot air discharged from the hot air outlet was returned to the hot air supply port and used again. The rotation speed of the fan provided between the hot air outlet and the hot air outlet was changed so that the average speed of the hot air at the hot air inlet and the hot air outlet was 1 m / sec. As shown in the schematic view of FIG. 7, of the side walls forming the side surface of the heat treatment chamber, a region from the side wall having no yarn introduction port or yarn ejection port to 0.3 m inside is defined as an untreated zone 10. . The partition plate 11 having the same number of stages as the yarns was installed in the untreated zone at the same height as the yarns.
The partition plate 11 had a width of 0.27 m and was continuously installed from the yarn introduction port to the yarn ejection port. The other conditions were the same as in Example 1.

In the untreated zone 10, the flow was retained by the partition plate 11 and the wind became almost zero. The wind speed in the region where the yarn traveled was 1.0 ± 0.2 m / sec, which was almost equal to the average speed at the hot air supply port and the hot air discharge port.
On the other hand, in Example 1, the wind speed in the untreated zone where no yarn is present is very high at 3 to 5 m / sec, and the wind velocity in the region where the yarn is traveling is 0.9 ± 0.2 m / sec, and hot air is supplied. It was slightly slower than the average speed at the mouth and hot air outlet.

As in Example 1, the temperature inside the heat treatment chamber was measured. As a result, point A: 247 ° C., point B: 248 ° C., point C:
245 ° C., D point: 249 ° C., E point, 249 ° C., and the maximum difference from the set temperature (average temperature of hot air supply port 250 ° C.) was 5 ° C.

As described above, according to the present invention, not only the temperature unevenness in the heat treatment chamber but also the wind speed unevenness is reduced, so that the flapping of the yarn is reduced and the process stability is improved.

[0058]

As described above, according to the heat treatment furnace of the present invention, hot air outflow from the heat treatment chamber and outside air inflow into the heat treatment chamber can be prevented without installing special additional equipment, and It is possible to reduce temperature unevenness, ensure process stability, and reduce manufacturing costs.

Further, since the temperature uniformity in the heat treatment chamber is excellent, the power consumption of the heater required when circulating hot air is reduced, resulting in an energy saving effect.

Further, in the heat treatment chamber, the pressure gradient generated by the buoyancy acting on the hot air and the pressure gradient generated by the resistance when the hot air passes through the yarns cancel each other, so that the temperature uniformity in the heat treatment chamber is not deteriorated. It is possible to increase the number of yarn steps and improve productivity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a heat treatment furnace according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a heat treatment furnace according to an embodiment of the present invention, and is a vertical cross-sectional view of FIG.

FIG. 3 is a partial sectional view showing an example of a grooved guide roll.

FIG. 4 is a schematic configuration diagram of a heat treatment furnace according to an embodiment of the present invention.

FIG. 5 is a general form of a conventionally used heat treatment furnace.

FIG. 6 is an embodiment of an analytical model used for obtaining a pressure drop amount per one stage of a yarn generated when hot air passes through the yarn by a numerical simulation.

7 is a schematic configuration diagram of a heat treatment furnace according to an embodiment of the present invention, and is a vertical cross-sectional view of FIG.

[Explanation of symbols]

1: Heat treatment chamber 2: Hot air outlet 3: Hot air supply port 4: Yarn inlet port 5: Yarn outlet port 6: Yarn 7: Guide roller 8: Fan 9: Heater 10: Untreated zone 11: Partition plate Ph : Yarn pitch Pv in the horizontal plane: yarn pitch P0 in the vertical direction P: pressure in the atmosphere outside the furnace P1: pressure in the upper part of the heat treatment chamber P2: pressure in the lower part of the heat treatment chamber ΔP: yarn generated when hot air passes through the yarn Pressure drop amount per stage F: Buoyancy acting on hot air g: Gravity acceleration magnitude ρ0: Outside atmosphere density ρh: Hot air density U: Average hot air velocity

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3B154 AA14 AB09 BA60 BB12 BB76                       BB77 BC01 BC11 BC17 BC22                       BC28 BC47 CA08 CA37 CA39                       CA42 DA24                 4L037 CS02 CT11 CT12 CT42 FA01                       PA53 PS02

Claims (12)

[Claims] 1. A heat treatment chamber, a hot air discharge port provided at an upper side of the heat treatment chamber and a hot air supply port provided at a lower side thereof, and a yarn introduction port and a yarn discharge port provided at a side of the heat treatment chamber. And having the yarn run horizontally in the heat treatment chamber,
A heat treatment furnace characterized in that hot air is blown onto the yarn from below to perform heat treatment. 2. A plurality of yarns are introduced into a heat treatment chamber so as to keep an arbitrary pitch Ph in a horizontal plane, and an arbitrary pitch Pv is set in the vertical direction of the heat treatment chamber while repeatedly entering and leaving the heat treatment chamber. The heat treatment furnace according to claim 1, wherein the heat treatment furnace is maintained. 3. A pressure drop amount when hot air passes through the yarn is ΔP (Pa), and a buoyancy force generated in the hot air based on the difference between the density of the atmosphere outside the furnace and the density of the hot air is F (N / m3), When the vertical yarn pitch is Pv (m), F × Pv / ΔP
So that it falls within the range of 0.7 to 1.6, the flow velocity of the hot air,
The heat treatment furnace according to claim 2, wherein at least one condition selected from the temperature of the hot air and the yarn pitches Ph and Pv is adjusted. 4. The flow velocity of hot air, the temperature of hot air, and the pitch P of yarns so that the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P2 in the lower part of the heat treatment chamber is −9 Pa ≦ P1−P2 ≦ 6 Pa.
The heat treatment furnace according to claim 2, wherein at least one condition selected from h and Pv is adjusted. 5. If the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P2 in the lower part of the heat treatment chamber is P1-P2> 6 Pa, the flow velocity of hot air is adjusted so as to increase, and P1-P2 <-9P.
The heat treatment furnace according to claim 1 or 2, further comprising: a means for adjusting the flow velocity of the hot air to be small in the case of "a". 6. If the relationship between the pressure P1 in the upper part of the heat treatment chamber and the pressure P0 in the atmosphere outside the furnace is P1-P0> 3 Pa, the flow velocity of hot air is adjusted to be high, and P1-P0 <-5 Pa.
In this case, the heat treatment furnace according to claim 1 or 2, further comprising means for adjusting the flow velocity of the hot air to be small. 7. If the relationship between the pressure P2 in the lower part of the heat treatment chamber and the pressure P0 in the atmosphere outside the furnace is P2-P0 <-3 Pa, the flow velocity of hot air is adjusted to be high, and P2-P0> 4 Pa.
In this case, the heat treatment furnace according to claim 1 or 2, further comprising means for adjusting the flow velocity of the hot air to be small. 8. When hot air outflow from the yarn inlet or yarn outlet in the upper half of the heat treatment chamber to the outside of the heat treatment chamber is observed, the flow velocity of the hot air is adjusted so as to increase, and The means for adjusting the flow velocity of the hot air to be small when hot air outflow to the outside of the heat treatment chamber from the yarn introduction port or yarn ejection port in the half is observed. The heat treatment furnace described. 9. The heat treatment furnace according to claim 1, further comprising means for adjusting the flow velocity of the hot air so that the temperature of the hot air discharged from the hot air outlet is maximized. 10. The untreated zone between the yarn and the side wall constituting the side surface of the heat treatment chamber has at least one partition plate installed in the horizontal direction in the vertical direction. The heat treatment furnace according to any one of 1. 11. The heat treatment furnace according to any one of claims 1 to 10, wherein the heat treatment furnace is a flameproofing furnace used for producing carbon fibers. 12. A method for producing a carbon fiber, which comprises using the flameproofing furnace according to claim 11.