Thermal Abatement of Perfluorocompounds with plasma torches

Abstract

Perfluorocompounds (PFCs) have long lifetimes and high global-warming potentials. PFCs include CF4, C2F6, C3F8, CHF3, SF6, NF3, etc., which are widely used in the electronic industries. Although the atmospheric concentrations of PFCs are currently much lower than CO2, the annually increasing rate of CF4 and SF6 are 3.3 and 12 times higher than CO2, respectively. A thermal plasma torch can offer an extremely high temperature stream for thermal decomposition of PFCs, and is regarded as a state-of-the-art technology for PFC emission control. In the study a thermal plasma torch is designed and experimentally tested for PFC abatements. Results show that PFC abatements are mainly determined by the plasma power, gas flow rate, and PFC’s concentration. The effects of operational parameters are further evaluated by the multiple regressions and the sensitivity analysis. For CF4, the most significant factor to the removal efficiency is the plasma power, and the flow rate plays a negative role. In addition, the most sensitive factor to the energy efficiency goes to the CF4 concentration. There is a trade-off between abatement efficiency and the energy efficiency. Thermal plasma torches can easily achieve high PFCs abatement efficiencies by an increase of plasma power. From an energy viewpoint, a thermal PFCs abatement system is better operated for streams with higher PFC concentrations. Therefore, installation of a PFCs concentrated unit in front of thermal plasma torch should be a good option in viewpoint of both abatement efficiency and energy efficiency.