The present invention relates to the processing and treatment of filaments for the manufacture of carbon fiber, proposing an oven with improved structural characteristics that assures that the filaments inside the oven remain parallel during the entire treatment process, preventing them from becoming deformed or from coming into contact with one another. The oven is configured for manufacturing carbon fiber from filaments of a precursor such as polyacrylonitrile (PAN), although the application thereof to this type of polymer is in no way limiting, and the invention may be applied for the manufacture of filaments of other alternative precursors, such as lignin, polyolefins or others having similar characteristics, for example.
The process of manufacturing carbon fiber from a precursor such as polyacrylonitrile (PAN) essentially comprises a stabilization/oxidation step, a carbonization step, and a surface treatment step. Additionally, when trying to obtain a high-performance fiber, a graphitization step can be added before the surface treatment step, so a graphite fiber is obtained fiber of graphite.
During the stabilization/oxidation step, the PAN precursor undergoes a first transformation to an oxidized state, known as OPAN or oxidized polyacrylonitrile, by means of a double cyclization and dehydrogenation reaction. In addition, a continuous loop structure of hexagonal carbon rings is obtained in the carbonization step from the OPAN. This step is sub-divided into two phases, one at a lower temperature, in which a pyridine structure is formed, and another at a higher temperature, in which the structure collapses into a turbostratic structure.
Both stabilization/oxidation and carbonization are carried out at high temperatures, which are less than 300° C. in the stabilization/oxidation process and which may reach up to 1800° C. or higher in the carbonization process. Said processes are carried out in specific ovens, such as, for example, the oven for manufacturing carbon fiber described in Spanish patent ES 2,528,068 B1 belonging to the same applicant as the present invention.
Said oven comprises therein modules in which the filaments are treated for the transformation thereof into carbon fiber, and conduction means for conducting the filaments formed by an assembly of rotary supports which can be displaced with respect to one another, between which the filaments are passed, which define a height-adjustable storage system for the filaments inside the oven. With this roller configuration, the filaments are vertically arranged inside the modules, remaining parallel to one another as they pass back and forth.
The vertical arrangement allows increasing the filament storage capacity inside the oven, thereby reducing the floor area occupied by same, and therefore reducing the cost of the carbon fiber manufacturing installation. Furthermore, the height-adjustable storage allows regulating the dwell time of the filaments inside the different modules of the oven according to the needs required by the precursor for the manufacture of the carbon fiber.
However, to maximize filament storage capacity and occupy the minimum surface area, ovens of this type have a structure having a height that is much greater than its width, such that the greater the height of the oven, a greater storage capacity is obtained. This structure can present problems relating to stability, since primarily due to adverse weather conditions where the oven is arranged, such as wind, and due to the height and weight of the oven itself, the upper part of the oven may sway back and forth. This swaying causes a lateral displacement of the upper part of the oven that may affect the parallel state of the filaments, such that the filaments may become deformed, or even come into contact with one another.
An alternative oven configuration that allows assuring that the filaments remain parallel to one another throughout the entire treatment process is therefore necessary.
According to the invention, an oven for manufacturing filaments is proposed which is configured for assuring that the filaments remaining parallel to one another as they pass through the inside of the oven when unwanted movements of the upper part of the oven occur, preventing the filaments from becoming deformed or from being able to come into contact with one another.
The oven for manufacturing filaments comprises:
With this oven configuration, it is assured that any movement of the second end of the oven body is transmitted in an identical manner to the platform of the first end of the oven body, such that the vertically arranged filaments are kept tensioned at all times between the first end and the second end of the oven body, the filaments remaining parallel to one another at all times, and preventing them from becoming deformed or from coming into contact with one another.
The attachment means comprise at one of the ends thereof first anchoring points for the fixing thereof to the platform of the first end of the oven body, and at the opposite end they comprise second anchoring points for the fixing thereof to the second end of the oven body.
The anchoring points are distributed in at least two rows parallel to one another, where the anchoring points of each row are aligned with one another, and where the anchoring points of the first row are intercalated with respect to the anchoring points of the second row. This distribution in at least two rows, with the anchoring points of each row intercalated with respect to one another, allows improving the transmission of stresses from the second end of the oven body to the platform, thereby assuring that the platform faithfully reproduces the movements of the second end of the oven body. Therefore, the conduction means carrying the filaments move as a single assembly, preventing deformation of the filaments.
According to a preferred embodiment, each first anchoring point comprises a frustoconical body that is inserted in a reciprocal housing of the platform, whereas each second anchoring point comprises an elastic body which is fixed to the second end of the oven body and which is configured for allowing radial play and pivotal play with respect to the longitudinal axis of the attachment means to which it is attached. Furthermore, the second end of the oven body comprises housings for the passage of the attachment means, where the housings have a diameter that is larger than the diameter of the attachment means passed through the housing. Excess straining in the fixing of the second anchoring points are thereby prevented, which could affect the structural integrity of the attachment means, which could even cause the breaking thereof, since it is precisely this area of the structure of the oven that withstands the highest amount of stresses when a movement of the second end of the oven body occurs.
The platform of the first end of the oven body comprises an arm which is connected to a support base by means of an articulation provided with an axis of rotation. The articulation has a spherical shape that fits in reciprocal gaps of the support base, such that the platform is susceptible to rotating and pivoting with respect to the axis of rotation of the articulation, where any movement originating at the second end of the oven body may be reproduced.
The conduction means for conducting the filaments are arranged inside modules dividing the inside of the oven into different steps of the treatment of the filaments. The modules comprise a structure through which the attachment means pass, where the modules are supported on the platform of the first end of the oven body and are attached to the second end of the oven body through the attachment means. In this way, the attachment means also transmit the movements of the second end of the oven body to the modules incorporating the conduction means for conducting the filaments, likewise assuring that the modules remain vertically arrange at all times between the first end and the second end of the oven body.
The modules are arranged on the platform in columns of modules, each of said columns of modules comprising a front access door that can be driven by driving means, which consist of cylinders which are connected at the free end thereof to the front access door and fixed at the other end thereof to the cross beam. These doors are provided to make access to the inside of the modules easier and to allow carrying out cleaning or maintenance tasks.
The oven additionally comprises sensor means which are configured for measuring the movements of the second end of the oven body and displacement means which are configured for moving the platform depending on the movements measured by the sensor means. With this solution, the attachment means are partially released in the transmission of the movement to the platform, so the service life thereof is increased and the response rate of the entire assembly is improved.
An oven for manufacturing carbon fiber filaments is thereby obtained, which oven, due to its constructive and functional characteristics, allows assuring a suitable passage of the filaments through the inside of the oven regardless of the movements that may originate in the structure of the oven, the filaments remaining parallel to one another at all times, preventing them from becoming deformed or from coming into contact with one another.
The invention relates to an oven for manufacturing filaments, which is particularly configured for the application thereof in the manufacture of carbon fiber filaments from the treatment of polyacrylonitrile (PAN) filaments, without this application being limiting.
The oven comprises an oven body (1) of a rectangular longitudinal section having a height that is considerably greater than its width, similar to a wind-driven power generator tower, as shown in the partial section view of
The oven body (1) has an elongated shape with a first end (1.1) and a second end (1.2) opposite the first end (1.1). As shown in the drawings, the first end (1.1) corresponds with the lower part of the oven, and the second end (1.2) corresponds with the upper part of the oven, although the second end (1.2) of the oven body (1) could be any intermediate point located between the lower part and the upper part of the oven body (1).
At the first end (1.1) of the oven body (1), there is arranged an inlet (1.3) for the untreated filaments, and on the opposite side of the first end (1.1) there is arranged an outlet (1.4) for the treated filaments after they have circulated inside the oven after having successively passed back and forth therein, and after having been subjected to stabilization, oxidation, and carbonization steps for the transformation thereof into carbon fiber. At the second end (1.2) of the upper part of the oven body (1) there is arranged an outlet for the circulated gases (1.5) used in the filament treatment steps.
Inside the oven body (1) there is arranged a storage system for storing the filaments comprising conduction means (2) through which the filaments are passed for conducting them through the inside of the oven in the successive back and forth passages between the inlet (1.3) and the outlet (1.4) of the oven body (1).
The conduction means (2) comprise first rotary supports (2.1) formed by vertically arranged rollers and second rotary supports (2.2) likewise formed by other vertically arranged rollers. The first rotary supports (2.1) are connected to the first end (1.1) of the oven body (1), whereas the second rotary supports (2.2) are connected to the second end (1.2) of the oven body (1).
The rotary supports (2.1, 2.2) can be displaced with respect to one another in the vertical direction, such that at least one of the rotary supports (2.1, 2.2) can be displaced vertically with respect to the other rotary support (2.1, 2.2). As can be seen in the examples of
The second rotary supports (2.2) may be adjusted in height with respect to one another, such that the variable displacement in the vertical direction of the rotary supports (2.2) allows the treatment time in each of the steps inside the oven to remain constant for any rate of supply of the filaments, which is a feature that is beneficial to the startup and shutdown processes, preventing the loss of large amounts of material due to an incomplete filament treatment.
With this arrangement, in order to thread the filaments between the conduction means (2), firstly the second rotary supports (2.2) are displaced to the first end (1.1) of the oven body (1) in order to be intercalated between the first rotary supports (2.1), then the filaments are introduced through the inlet (1.3), passing them between the rotary supports (2.1, 2.2) and taking them out through the outlet (1.4), as shown in
As depicted in
To assure that the filaments remain vertically arranged between the first end (1.1) and the second end (1.2) of the oven body (1) and are suitably parallel to one another, the oven of the invention additionally comprises a platform (3) and attachment means (4). The platform (3) is pivotably arranged at the first end (1.1) of the oven body (1), and the conduction means (2) for conducting the filaments are arranged thereon, whereas the attachment means (4) attach the platform (3) to the second end (1.2) of oven body (1), transferring the movements of the second end (1.2) of oven body (1) to the platform (3).
The swaying of the second end (1.2) of the oven body (1) is thereby transmitted to the platform (3) supporting the conduction means (2) for conducting the filaments through the attachment means (4), thereby assuring at all times that the filaments remain vertically arranged between the first end (1.1) and the second end (1.2) of the oven body (1), being suitably parallel to one another, preventing them from becoming deformed or from coming into contact with one another, as can be seen in
It has been provided that the attachment means (4) are mechanical cables, which are not entirely rigid but rather a certain degree of flexibility to enable absorbing the tensile stresses to which the oven body (1) is subjected during swaying, such as, for example, cables with interlocking steel tow ropes.
The oven body (1) comprises therein modules (5) in which the stabilization, oxidation, and carbonization steps are carried out for treating the filaments and transforming them into carbon fiber. The modules (5) comprise therein the conduction means (2) for conducting the filaments and have hot gas inlets (not depicted in the drawings) for creating the conditions necessary for treating the filaments in each step.
The modules (5) comprise a structure incorporating refractory material to reduce energy losses due to heat leaking out between the modules (5) and the outside, and between the modules (5) themselves. The structure of the modules is used for passing the attachment means (4) through same, such that the stresses of the second end (1.2) of the oven body (1) are transmitted to the modules (5) through the attachment means (4).
The modules (5) comprising the conduction means (2) are arranged between the first end (1.1) and the second end (1.2) of the oven body (1). The modules (5) are supported on the platform (3) of the first end (1.1) of the oven body (1), whereas in relation to the second end (1.2) of the oven body (1), the attachment of the modules (5) to the second end of the oven body (1) is performed by attachment means (4), as can be seen in detail in
It has been provided that the modules (5) through which the attachment means (4) are guided are blocks having small dimensions, preferably less than 1 meter in height. The modules (5) are arranged parallel to one another and stacked one on top of another, favoring their arrangement and alignment for introducing the attachment means (4). Between the blocks forming the modules (5) there is arranged an elastically deformable material which allows offsetting the thermal expansion differences existing between the material with which the attachment means (4) are made and the material forming the modules (5).
The second end (1.2) of the oven body (1) comprises a cross beam (6), preferably an H-cross beam, which is integrally attached by both ends to the oven body (1), such that the stresses to which the oven body (1) is subjected are transmitted directly to the cross beam (6).
The attachment means (4) have at one of the ends thereof first anchoring points (7) for the fixing thereof to the platform (3) of the first end (1.1) of the oven body (1), and at the opposite ends the attachment means (4) have second anchoring points (8) for the fixing thereof to the cross beam (6) of the second end (1.2) of the oven body (1). The anchoring points (7, 8) have a particular distribution that improves the transmission of movements from the cross beam (6) to the platform (3).
As can be seen in detail in
This distribution of at least two rows (f1, f2) obviously transmits stresses better than in the case of using a single row of anchoring points aligned in the longitudinal direction (x), where the transmission of movements would only be effective in the longitudinal direction (x), and would not be as effective in the transverse direction (y). Nevertheless, since the cross beam (6) can sway in any direction, the platform (3) must also pivot in any direction to enable reproducing the movements of the cross beam (6); as a result, it has been provided that in addition to the distribution of at least two rows (f1, f2), the first anchoring points (7) have a staggered distribution, in which the anchoring points (7) of the first row (f1) are intercalated with respect to the anchoring points (7) of the second row (f2). This intercalated distribution with respect to the anchoring points (7) of each row (f1, f2) improves the transmission of stresses in all directions, while at the same time minimizing the number of necessary anchoring points.
The distribution of the second anchoring points (8) in the cross beam (6) of the second end (1.2) of the oven body (1) is identical to the distribution of the first anchoring points (7) described above.
It can also be observed in
With this being the case, for installing the attachment means (4), said means are first introduced through the housings of the platform (3) and then they are introduced into the housings (6.1) of the cross beam (6) of the second end (1.2) of the oven body (1), after which the second anchoring points (8) are tightened for tensioning the attachment means (4), the latter thereby being axially retained by traction between the platform (3) and the second end (1.2) of the oven body (1).
The platform (3) comprises a triangular-shaped arm (3.1) which is connected in its lower vertex, by means of an articulation (3.3), to a support base (3.2) provided with two flaps arranged on the floor of the oven. The articulation (3.3) has an axis of rotation (w) which allows the pivoting of the platform (3) with respect to the support base (3.2), and it has a spherical shape that fits in reciprocal gaps of the support base (3.2), such that the articulation (3.3) allows the platform (3) to pivot with respect to the support base (3.3). Specifically, as shown in
The modules (5) are arranged in columns of modules (5), one module (5) being arranged on top of another, in which each of said columns of modules (5) comprises a front access door (9) that allows accessing the inside of the modules (5) to carryout cleaning or maintenance tasks therein. Each of said doors (9) can opened by driving means (10), which according to the example shown in
Additionally, it has been provided that at the second end (1.2) of the oven body (1) there are arranged sensor means for measuring the movements of the second end (1.2) of the oven body (1), and displacement means moving the platform (3) depending on the movements measured by the sensor means. The sensor means may be any type of means that allow detecting the movements of the second end (1.2) of the oven body (1), such as, for example, accelerometers arranged in the cross beam (6), or elements for measuring the distance between the oven body (1) and the modules (5). The displacement means can be formed by a motor acting directly on the articulation (3.3) of the platform (3). The platform (3) can thereby be acted on immediately once a movement of the second end (1.2) of the oven body (1) is detected, so it is achieved that the attachment means (4), and primarily the second anchoring points (8), withstand fewer stresses when transmitting the movements to the platform (3).
Number | Date | Country | Kind |
---|---|---|---|
P201630306 | Mar 2016 | ES | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/ES2017/070048 | 1/27/2017 | WO | 00 |