Numerical analysis on a thermal plasma reactor for HFC-23 treatment

It was simulated that thermal flow characteristics inside a thermal plasma reactor for an abatement ofHFC-23 (trifluoromethane, CHF3) which is a kind of greenhouse gas. Effects of arc current and length of reaction tubes on the decomposition process were numerically analyzed to find out a suitable plasma torch operating condition and an optimal reactor design. Numerical results were in good agreements with experimental results on measured temperature at reactor exit and a damaged appearance of the inner reaction tube after the practical decomposition process. A sufficiently large area and high temperature over 1500 K for HFC-23 decomposition was predicted in the torch operation with an arc current of 50 A. In this condition, a high decomposition rate over 99.5%was achieved in spite of a short residence time estimated around 50 ms. And it was revealed that not only the length of the inner reaction tube which is continuously contact with high heat flux from the thermal plasma jet but also the outer tube length is important for a durable operation of the reactor system.

► Thermal plasma reactor for HFC-23 treatment was precisely simulated.
► Two tubes are placed in the reactor to provide high temperature environment over 1500 K and to introduce waste and reactive gases, respectively.
► Melting issue arose in inner reaction tube which is directly contact with thermal plasma jet, was solved by optimizing the length of outer tube with high treatment efficiency over 99.5%.