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Reducing emissions from the manufacturing of carbon fibers

By Tetsuo Satoh |

Carbon fibers are typically fabricated by the oxidation of a polymeric fiber, such as polyacrylonitrile (PAN) at 200–300°C, which generates a large amount of exhaust air containing several hundred parts per million (ppm) of hydrogen cyanide and ammonia. This is followed by a carbonization process at 1,000–1,200°C, which takes place under an inert atmosphere, such as N2. The second step generates a smaller amount of exhaust N2, but with high concentrations of HCN and NH3. Conventional treatment systems are unable to handle both the destruction of HCN and NH3 emissions while suppressing the generation of oxides of nitrogen (NOx). To solve this problem, Taiyo Nippon Sanso Ltd. (Tokyo, Japan; www.tn-sanso.co.jp) has developed a system called Innova-Flash, which uses a two-step oxidation process to treat both exhaust streams. In the first step, the highly concentrated HCN/NH3-laden N2 undergoes a high-temperature treatment under reductive conditions. In the second step, a low-temperature oxidation process removes the low concentration of HCN and NH3 in the air exhaust. By injecting the combustion gas (which also contains fuel components) generated in the first step into the second step, energy savings of approximately 50% are achieved,…
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