EP2611955A1

EP2611955A1 - Oxidation furnace

Info

Publication number: EP2611955A1
Application number: EP11752106.2A
Authority: EP
Inventors: Karl Berner
Original assignee: Eisenmann SE
Current assignee: Eisenmann SE
Priority date: 2010-09-03
Filing date: 2011-08-16
Publication date: 2013-07-10
Also published as: JP6034289B2; CN103080391B; DE102010044296B3; US20130171578A1; BR112013005187A8; BR112013005187A2; JP2013542331A; CN103080391A; RU2594415C2; RU2013109001A; WO2012028260A1; US9303921B2

Abstract

The invention relates to an oxidation furnace (1) for the oxidative treatment of fibers (20), in particular for producing carbon fibers. In a known manner, the furnace has a processing chamber (6) which can be found in the interior of a housing (2); at least one blowing device (13); at least one suction device (14); at least one ventilator (21) that circulates the hot air through the blowing device (13), the processing chamber (6), and the suction device (14); and at least one heating device (18) that lies in the flow path of the hot circulated air. Deviating rollers (24, 25, 26, 32) guide the fibers (20) in a serpentine manner through the processing chamber (6) such that the fibers lie next to one another as a carpet, the fiber carpet (20) being stretched between each opposing deviating roller (24, 25, 26) over one plane. The air in the processing chamber (6) crosses the planes over which the fiber carpet (20) is stretched at an angle that differs from 0° and 90° using special means (33). In this manner, a better heat exchange between the hot oxidative air and the fibers (20) is achieved.

Description

Oxidation

The invention relates to an oxidation furnace for the oxidative treatment of fibers, in particular for the production of carbon fibers, with a) a housing which is gas-tight except for passage areas for the carbon fibers; b) a process space located in the interior of the housing; c) at least one blowing device, with which

hot air is blown into the process space; d) at least one suction device which is hot

Air from the process room sucks; e) at least one fan containing the hot air

circulated through the injection device, the process chamber and the suction device; f) at least one heating device located in the flow path of the hot circulating air; d) deflection rollers, which guide the fibers adjacent to each other in a serpentine manner as a carpet through the process space, wherein the fiber carpet spans one plane between opposite deflection rollers.

In known oxidation furnaces of this type, the various, superimposed planes of the fiber carpet run pichs horizontally and are parallel to the flow direction of the hot, oxygen-containing air. This has the consequence that the air flow on the heating and cooling of the

Fibers participate only in its marginal layers adjacent to the fiber carpet. Due to the parallel flow, a boundary layer is formed on the surface of the fibers, which reduces the heat transfer. The core of the air flow does not participate in the heat transfer due to the parallel flow. There are high differences between the air inlet and outlet air temperature near the fibers, which in turn leads to high temperature differences within the fiber carpet. The fundamental

Possibility to increase the heat transfer by raising the air velocity, there are limits, as by the increasing movement of the fibers damage

same threatens, for example, by colliding.

In an alternative construction of the aforementioned known oxidation ovens, the entire air flow

vertically through the different superimposed ones

Layers of fiber carpet led. This leads to a better heat transfer. Aufrgund the air supply or air extraction, however, increases the height. Object of the present invention is to provide an oxidation furnace of the type mentioned, in which improves at low height of the heat transfer between the air and the fibers and the temperature of the fibers in the process room is further homogenized.

This object is achieved in that

Means are provided which ensure that

the air in the process room that from the fiber carpet

spanned levels at an angle of 0 ° and 90 ° is different, crosses.

The oblique flow of the air obtained in this way in relation to the planes of the fiber carpet results in a better temperature uniformity, since the fiber carpet is subjected to the same temperature over the entire length between the injection device and the suction device. This means better process management with a better process result. It is the entire recirculated air used for heat absorption or heat dissipation; there are none between the levels of the fiber carpet

uninvolved air currents. A lower volume flow is sufficient to achieve the same result. This

not only saves energy, but also allows for smaller dimensions of the oxidation furnace.

In an advantageous embodiment of the invention, the means comprise at least two air baffles.

Particularly favorable are a plurality of air baffles, each extending in the spaces between the planar regions of the serpentine fiber carpet between the injection device and the suction device. These baffles give the air flow not only the

desired direction. They also act as radiation surfaces, which are used to heat up the threads as well

contribute to the dissipation of the exothermic heat that arises during the oxidation. Also in this way, the temperature difference between the circulated air and the

Reduced fibers. At the same time, the air baffles take over the function of the fiber guide profiles, which were previously used to prevent contact or entanglement of fibers in fiber breakage. Alternatively or additionally, as a means of achieving the desired relative orientations of air flow and fiber carpet levels, an additional air flow having a vertical directional component and in the process space the first, between the

Inflator and the suction device extending airflow superimposed. The angle at which the "effective" air flow created by the superposition crosses the planes spanned by the fiber carpet can be adjusted in this embodiment of the invention by the ratio of the flow velocities in the two flows; this embodiment is so

far more variable than the one that works with baffles. Again alternatively or additionally, the means in question may also consist in deflection rollers which are tilted relative to the vertical, that the planes spanned by the fiber carpet running between them are tilted with respect to the horizontal.

The inventive concept can be both there

where the main flow direction of the air is that of the longitudinal direction of the oxidation furnace between the inlet region and the outlet region, as well as where the main flow direction of the air is perpendicular to the

Longitudinal direction of the oxidation furnace is. In the first case, the angle under which the air should be the plane of the

Fiber carpet crosses between 0.8 ° and 2 °, preferably 1 °, in the second case between 2 ° and 20 °, preferably 4 °, amount.

Embodiments of the invention will be explained in more detail with reference to the drawing; FIG. 1 shows a vertical section through an oxidation furnace for the production of carbon fibers in furnace ^¬ longitudinal direction;

FIG. 2 shows a horizontal section through the oxidation furnace of FIG. 1 according to the line II-II there,

(Fiber carpet not drawn);

Figure 3 is a vertical section through the oxidation furnace of Figures 1 and 2 along the line III -III of Figure 1;

4 shows the circled on the left in Figure 1 area

a modified embodiment of an oxidation furnace;

FIG. 5 shows a vertical section, similar to FIG. 1

through an oxidation furnace with cross-flow of air; FIG. 6 shows a horizontal section through the oxidation furnace of FIG. 5 according to the line VI-VI there,

(Fiber carpet and pulleys not drawn);

Figure 7 is a vertical section through the oxidation furnace of Figure 5 according to the local line VII-VII;

FIGS. 8 to 10

in a more schematic schematization sections through alternative embodiments of an oxidation furnace, similar to FIG. 7.

1 to 3, in which a first embodiment of an oxidation furnace is shown, which is generally designated by the reference numeral 1 and for the production of carbon fibers is used. The oxidation furnace 1 comprises a housing 2, which in turn is composed of two vertical longitudinal walls 2a, 2b, two vertical end walls 2c, 2d, a top wall 2e and a bottom wall 2f. The housing 2 is with the exception of two areas 3, 4 in the end walls 2c and 2d, in which the treated

Fibers 20 are running and running and which are provided with special lock devices, gas-tight. As can be seen in particular from FIG. 2, the interior of the housing 2 is subdivided by a vertical partition 5 into the actual process space 6 and air ducts 7, 8, 9, 10, 11, 12 lying laterally therefrom. Overall, the interior of the oxidation furnace 1 is substantially mirror-symmetrical to that in FIG

2 indicated center plane S-S formed.

In the middle region of the process chamber 6 there is a blowing device provided overall with the reference numeral 13, which is explained in more detail below. In the two outer end areas of

In the interior of the housing 2, two opposing air circuits are maintained: starting, for example, from the suction devices 14, 15, the air is in the process chamber 6, respectively adjacent to the passage areas 3, 4 adjacent

2 arrows through the air ducts 7 and 12 to a filter 16 or 17 and then passed through a heating unit 18a and 18b in the air guide 8 and 11, respectively. From the air duct 8 and 11, the heated air from a fan 21a and 21b

sucked off and blown into the air ducts 9 and 10 respectively. From there, the air enters each half of the blowing device described in more detail below 13, from there in opposite directions flowing into the process space

6 and from there in more detail below

Way to the suction device 14 and 15, whereby the two air circuits are closed.

In the wall of the housing 2, two outlets 30a, 30b are provided in the region of the air guide chambers 8, 11. About this gas or air volumes can be dissipated, which arise either in the oxidation process or as fresh air through the passage areas 3, 4 in the

Access process space 6, so as to maintain the air balance in the oxidation furnace 1 upright. The discharged gases, which may also contain toxic components are fed to a thermal afterburning. The heat obtained can be used at least for preheating the fresh air supplied to the oxidation furnace 1.

The injection device 13 is constructed in detail as follows:

It comprises two "stacks" of blow boxes 31. Each of these blow boxes 31 has the shape of a hollow cuboid, wherein the longer dimension extends transversely to the longitudinal direction of the process space 6 over its entire width. The respective narrow sides of the injection boxes 31 facing the process space 6 are formed as perforated plates 31a. An exception here are the lowest blow boxes 31, each of which from the center of the oxidation furnace

1 pointing away narrow side is closed for reasons that will become apparent below.

In each case one end face of each injection box 31 is connected to the air guide space 9 or air guide space 10 in such a way that the one conveyed by the fan 21a or 21b Air in the interior of the respective injection box

31 is injected and from there on the perforated plates

31a can escape. The various blow boxes 31 in each of the two stacks are arranged one above the other at a slight distance. The two stacks of blow boxes 31, in turn, are also spaced apart, viewed in the longitudinal direction of the oven or in the direction of movement of the threads 20.

The two suction devices 14, 15 are essentially formed by a respective stack of suction boxes 19, which extend in a similar manner as the blow boxes 31 in the transverse direction through the entire process chamber 6 and formed at their transversely to the longitudinal extent of the process space 6 extending narrow sides as perforated plates 19a are. An exception here, for reasons becoming understandable below, the narrow side of the respective uppermost extraction boxes 19 pointing towards the middle of the furnace in the stack.

Between the upper edges of the outward facing

Narrow sides 31a of the blow boxes 31 and the lower

Edges of the narrow sides of the furnace facing the furnace

Extraction boxes 19 each extend planar air baffles 33rd

The fibers 20 to be treated are fed to the oxidation furnace 1 running parallel as a kind of "carpet" via a deflection roller 32 and thereby pass through a Zuluft- device 22, which is not interesting in the present context and serves to supply preheated fresh air to the process. The fibers 20 are then through the spaces between superimposed suction boxes 19, through the process space 6, through the spaces between superimposed blow boxes 31 in the Injection device 13, guided by the gap between superimposed suction boxes 19 at the opposite end of the process chamber 6 and by a further supply air - device 23.

The described passage of the fibers 20 through the process chamber 6 is serpentine repeated several times, including in both end portions of the oxidation furnace 1 more

with their axes parallel superimposed Umlenkrol- len 24, 25 are provided. Between the deflection rollers 32, 25, 24, 26 of the fiber carpet 20 each spans a plane. After the uppermost passage through the process space 6, the fibers 20 leave the oxidation furnace 1 and become

thereby guided over a further deflection roller 26.

During the serpentine passage of the fibers

20 through the process room 6, these become hotter,

oxygen-containing air flows around and thereby oxidizes.

This air emerges from the narrow sides 31a of the

Blowing boxes 31 in the space between two parallel baffles 33 and each passes to a pointing to the furnace center narrow side 19a of a suction box 19, namely to that narrow side 19a of that

Suction box 19, which is lower than the "floor" by a

Injection box 31 is.

The flow of the hot, oxygen-containing air produced in this way crosses the plane of the "fiber carpet" in this way, so it is no longer exactly horizontal but has a vertical component of the flow direction.

This has the consequence that the oxidizing furnace of known construction by the parallel flow of air and fibers entering boundary layer is avoided. The streaming

Rather, air penetrates the carpet of fibers 20 and also reaches the fibers 20 that are inside the fiber core. carpet 20 lie. The result is a better heat transfer, mainly to the internal fibers in the carpet 20, which in turn has a shorter procedural treatment time, a lower temperature difference between air temperature and fiber temperature, a homogenization of the fiber temperature within the fiber carpet 20 and thus ultimately a better fiber quality result. The fibers 20 are also acted upon by the oblique flow with air that comes directly from an injection box 31 and therefore on the entire length between the respective injection box 31 and the associated

Suction box 19 substantially the same temperature

has.

The air baffles 33 have additional functions:

So they serve on the one hand when heating the threads as beam surfaces and on the other hand, the exothermic heat generated during the oxidation of the fibers 20 through

Absorption of heat radiation from. In this way, the temperature difference between the fibers 20 and the circulated air is reduced, which allows a more accurate process control.

Finally, the air baffles 33 take over the function of Faserleitprofilen. Such separate guide profiles were required in known oxidation ovens. They completely prevent the contact and entanglement with other fibers when a fiber breaks. Broken fibers are completely absorbed by the baffles 33.

FIG. 4 shows the region of an oxidation opening on the left in FIG. 1 surrounded by a circle in an alternative embodiment. Corresponding parts of this Alternative embodiments are identified by the same reference numerals as in Figure 1, but increased by 100, and will not be described in detail. The same applies to those described below

Embodiments, where from reference to embodiment, the reference numerals are increased by 100 each.

In the exemplary embodiment of FIG. 4, the vertical component of the air flow is not achieved by air baffles, but rather in that a vertical air flow is additionally superimposed. For this purpose, air is blown into the process space 106 in the direction of the arrows 134 and sucked off in the lower region of the process space 106 in the direction of the arrows 135. As it enters the process chamber 106 and exits the process space 106, the air can pass through perforated plates 136, 137, which in the process of creating an obliquely opposite to the horizontal

Airflow are helpful. Whereas in the exemplary embodiments of an oxidation furnace 1 or 101 described above with reference to FIGS. 1 to 101, the hot, oxygen-containing air had a flow whose larger directional component pointed in the direction of movement of the threads 20, this is the case in the exemplary embodiments of the invention shown in FIGS to 10 are shown, differently. Here is the main flow direction of

Air substantially transverse to the direction of movement of the threads.

Reference is first made to Figures 5 to 7, in which a first, working with air transverse flow

Embodiment of an oxidation furnace 201 is shown.

When comparing FIG. 5 with FIG. 1, it is first of all noticeable that the middle blowing device 31 is in the position of the embodiment shown in FIG. Example of Figure 5 is missing. This is an immediate consequence of the fact that the main flow direction of the air does not run in the longitudinal direction of the oxidation furnace 201 but in its transverse direction. If suction boxes 219 are provided in both end regions of the housing 202, this serves for safety purposes, in order to prevent the escape of potentially air-containing gases via the passage regions 203, 204.

How the flow of the hot, oxygen-containing air in the embodiment of Figure 5 extends is best seen in Figures 6 and 7. For the description of the air circuits, let it be assumed that the suction device 214a is called "secondary suction device" for reasons that will become clear hereinafter. From this, the sucked air first enters the air duct 207 and mixes here with another air flow, as will be described below. The combined air streams then pass through a filter 216 and a heater 218, thereby entering the air guide 208. A portion of the air can, similar to the Ausführungsbeii- game of Figure 1, are withdrawn through an outlet 230 a. A fan 221 sucks the air out of the air-conducting space 208 and presses it into an air duct 209. This leads across the process space 206 to a lateral, wedge-shaped tapering downwards

Air distribution chamber 238, which serves as a blowing device 213 here. The process space 206 is bounded on this side by a perforated plate, so that the air guided into the air distribution space 238 can enter the process space 206.

The process space 206 is subdivided by a plurality of parallel air baffles 233. These air baffles 233 are different than the baffles 33 of the exemplary embodiment. les of Figure 1 is not inclined in the longitudinal direction of the oxidation furnace 201 but in the transverse direction. This has the consequence that the air entering via the air distribution space 238 into the spaces between the air baffles 233 is directed obliquely downwards, crossing the horizontal carpets of fibers 220 and in a similar manner as in the embodiment of Figure 1 for a good heat transfer to care. Otherwise, the effects are with the air duct and with the baffles

233 are connected, the same as in the embodiment of Figure 1.

On the opposite side, the intermediate spaces between the air guide plates 233 communicate with the air guide space 207 via another perforated plate, where the air, as mentioned above, mixes with the air coming from the secondary suction devices 214a, 215a. The air duct 207 in turn communicates with the suction side of the fan 221 as described above, so that the air duct 207 forms the "main exhaust" 214 of this embodiment.

In the embodiment of an oxidation furnace 301 shown schematically in FIG

omitted in the embodiment of Figure 4 obliquely directed baffles between the various serpentine fiber carpet 320 and instead used an additional air flow. This additional air is blown from above into the process chamber 306 in the direction of arrows 334, passing through a perforated plate

336, traversed at the lower end of the process chamber 306 another perforated plate 337 and is then in the sense

sucked off the arrows 335. By superimposing the introduced from the air distribution chamber 338, which represents the injection device 313, in the process chamber 306 and Resulting in the suction channel 339, which is the Hauptabsaugeinrichtung 314, air flowing on the one hand and the guided in the direction of arrows 334, 335 through the process chamber 306 second air flow results in an obliquely directed air flow, which is the carpet of fibers

320 with the above already mentioned advantages crosses.

Another way to create an air flow that does not flow parallel or perpendicular to the carpet of fibers is shown in FIG. In the embodiment described here, in turn, air baffles 433 are used, which, however, run horizontally. What is skewed is the carpet of fibers 420, which can be achieved, for example, by having the different pulleys on the opposite ones

Passage areas of the oxidation furnace 401 are made correspondingly inclined.

Finally, the exemplary embodiment of FIG. 10 completely dispenses with air guide plates and replaces them with an additional air flow, which is introduced from above into the process chamber 506 in the direction of the arrows 534, thereby passing through a perforated plate 536 which has parallel, obliquely arranged carpets Fibers 520 passes and is sucked off via a further perforated plate 537 in the direction of arrows 535. The results are similar to the embodiment of FIG. 8.

Claims

claims

An oxidation furnace for the oxidative treatment of fibers, in particular for the production of carbon fibers, with a) a housing which is gas-tight except for passage areas for the carbon fibers; b) a process space located in the interior of the housing; c) at least one blowing device, with which

Air from the process room sucks; e) at least one fan containing the hot air

circulated through the injection device, the process chamber and the suction device; f) at least one in the flow path of the hot circulated

Air lying heater; g) pulleys, which guide the fibers as a carpet next to each other in a serpentine manner through the process space, wherein the fiber carpet each spans a plane between opposing deflection rollers; characterized in that h) means (33; 134, 135; 233; 334, 335; 433; 534, 535) are provided, which ensure that the air in the process space (6; 106; 206; 306; 406; 506) the

of the fiber carpet (20; 120; 220; 320; 420; 520) at an angle other than 0 ° and 90 °.

2. Oxidat onsofen according to claim 1, characterized in that the means at least two air baffles (33;

233; 433).

An oxidation furnace according to claim 2, characterized in that said means comprise air baffles (33; 233; 433) disposed respectively in the spaces between the planar regions of the serpentine fiber carpet (20; 220; 420) between the blowing means (13; 213; 413)

and the suction device (14; 214; 414).

4. Oxidation furnace according to one of claims 1 to 3,

characterized in that the means comprise an additional flow of air (134, 135, 334, 335, 534, 535) having a vertical directional component and in the

Process room (106; 306; 506) the first, between the

Superimposed blowing device (113; 313; 513) and the suction device (114; 314; 514) extending air flow.

5. oxidation furnace according to one of the preceding claims, characterized in that the means deflecting rollers

(424, 425, 426, 432, 524, 525, 526, 532) which are tilted relative to the horizontal so that the planes spanned by the fiber carpet (420; 520) extending between them are tilted with respect to the horizontal.

6. Oxidation furnace according to one of the preceding claims, characterized in that the main flow direction the air is that of the longitudinal direction of the oxidation furnace (1; 101) between the opposite passage regions (3, 4; 103, 104).

7. oxidation furnace according to claim 6, characterized in that the angle between 0.8 ° and 3 °, preferably

1 °, is.

8. Oxidation furnace according to one of claims 1 to 5,

characterized in that the main flow direction of the air is perpendicular to the longitudinal direction of the oxidizing furnace (201; 301; 401; 501).

9. oxidation furnace according to claim 8, characterized in that the angle between 2 ° and 20 °, preferably 4 °.