Simulation and Experimental Study on the Degradation of the Greenhouse Gas Sf6 by Thermal Plasma

Abstract

SF 6 gas is widely used on many occasions especially in the power equipment, but it has been restricted since Kyoto Protocol as the strongest greenhouse gas. To reduce the SF 6 emission, several methods are now used such the recycling & purification and the SF 6 degradation. Considering the huge market of SF 6 and the recent demand in the field of power equipment, it is necessary to explore new ways to thoroughly destroy SF6. This work brought out the idea to degrade retired SF 6 by thermal plasma. A simplified kinetic model was established to predict the feasibility of this idea as well as the degradation products of SF 6 , and then the prototype of SF 6 degradation by thermal plasma was built and tested. In thermal plasma, SF 6 gradually decomposed into atoms, and then H 2 was added to capture the released F atoms to generate HF and also prevent the association reactions of SF 6 . In order to achieve the desired degradation effect, the reaction temperature and the mixing ratio of H 2 should be sufficiently high. However, excessive H 2 could generate the H 2 S, and excessive discharge power could decrease the energy yield. When the flow rate of SF 6 /H 2 was set as 8/30 L/min and the discharge current was set as 100A, the destruction removal efficiency (DRE) of SF 6 was 99.0% and the energy yield was 206 g/kWh. This work also discusses how to further treat the by-products such as HF and S from this prototype effectively.

Keywords: SF6, H2, degradation, thermal plasma, destruction removal efficiency, energy yield