JEC COMPOSITES MAGAZINE - Issue #63 - March 2011 - 98

carbon fibre
the possible challenges, a highly reliable line with extended uptimes is ensured by Fleissner’s long-standing experience in building fibre lines for PAN spinning as well as for several other fibre processes. The precursor line ends with the winding of the precursor tow, as the carbonization process runs at significantly lower speeds. (see Figure 2 for the entire precursor line) concepts, the highly efficient verticaldown flow concept is also available. As a result, individually tailored solutions are available to meet each customer’s specific needs. The next process, carbonization, is carried out in two steps. The first step takes place in a furnace up to 1000°C (LT furnace), which is directly followed by the hightemperature furnace (HT), which heats up to 1800°C. A further step is necessary for special carbon fibre applications: a graphitization process that follows the initial carbonization process at even higher temperatures. This optional phase takes place in an ultra-high-temperature furnace (UHT) operating at temperatures up to 2600°C. Ruhstrat’s furnaces reach a temperature consistency of +/- 3°C and have a much lower connection power (up to 50%) than similar units available on the market. For the past 100 years, Ruhstrat has developed their experience in high-temperature technology and has become a recognized leader in the field. The process of converting a PAN precursor material into carbon fibre generates exhaust air containing hydrogen cyanide, ammonium, silicon and tar residues. Lowconcentration exhaust air streams are reliably purified using the Eisenmann regenerative thermal oxidizer with an integrated heat recovery system. More concentrated exhaust air streams are purified in a highturbulence combustion chamber. The heat required to oxidize the pollutants is re-used by individuallydesigned energy recovery systems, thus optimizing the use of all the energy resources. After the carbonization, fibre tows must be uniformly roughened over the entire cross-sectional area of the tow using an electrochemical process. Following an intermediate drying phase, the final process step consists in applying a sizing allowing for yarn bundling, which also acts as a coating to optimize the fibre-matrix composition. Both steps are managed by proven modular Fleissner units utilizing the latest achievements in this technology. The finished tows are wound parallel onto manageable bobbins suited for the next intended purpose.

Carbonization line
Consequently, the carbonization line starts with the unwinding of the precursor tow. During the carbonization process, every single precursor tow is transformed into a separate carbon fibre tow. Again, Fleissner’s expertise and knowledge of tow handling ensure strictly parallel tow guiding and the overall process control in the following steps.

Conclusion
Today, building complete systems for carbon fibre production is much less complicated than it was only few years ago. By choosing the right supplier, such as the Alliance formed by Trützschler, Eisenmann, Ruhstrat and their partners, fibre producers or potential fibre producers can benefit from highly-developed components, closely coordinated by the Alliance with an overall process control. Based on its experience, the Alliance offers equipment from lab-scale up to industrial production lines with an output up to 2000 tons of carbon fibre per year. All the equipment is fully complementary and the interfaces are defined with precision. Additional partners such as EPC Industrial Engineering, for the polymerization process, complete the portfolio. n
Contact: erwin.glawion@truetzschler.de More information: www.truetzschler.de www.eisenmann.com www.ruhstrat.com

Fig.3: Lay-out of a Carbonization Line

jec composites magazine / No63 March 2011

The first fibre-modifying process step in the carbonization line uses specifically-designed oven systems for the oxidation or stabilization of the PAN precursor. High-precision air flow patterns are required to uniformly remove the heat generated in the fibre tow band during the exothermal oxidation process. To ensure constant and reproducible fibre quality, it is essential to have a highly uniform temperature at any given point in the ovens to achieve equalized thermal treatment of all tows. Eisenmann manufactures oxidation ovens which are distinguished by their consistent airflow and temperature uniformity. Depending on the fibre type, customers can choose between different air flow concepts. In addition to the conventional crossflow and centre-to-end air flow

http://www.truetzschler.de http://www.eisenmann.com http://www.ruhstrat.com

JEC COMPOSITES MAGAZINE - Issue #63 - March 2011

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #63 - March 2011