Comparison of the Effect of H2 and O2 on SF6 Degradation by Hot Plasma

SF6 has good insulation performance and arc extinguishing performance, which is more and more widely used in the power industry, and its emissions are also rising year by year. SF6 has a very high GWP value, 23,900 times that of CO2, and it is almost impossible to decompose in nature, so the harmless degradation of SF6 is extra important. In this work, we carried out flow degradation treatment of SF6 through a degradation device with hot plasma torch as the core, which was developed and designed by ourselves. Meanwhile, the degradation rate, toxicity and corrosion of degradation products were compared and analyzed under the condition that H2 and O2 were used as active gases respectively. The results show that the degradation rate of O2 as the active gas is up to 96.17%, and the degradation rate of H2 is up to 99%. The results of gas chromatograph, DRX and FTIR showed that the components of SF6 were S and HF in the presence of H2, and the main degradation products of SF6 were SO2F2, SO2 and SOF2 in the presence of O2. Both of the degradation products with the two gases have certain toxicity and corrosion, so we added a lye pond at the tail of the device to conduct harmless treatment of harmful products. The composition of the gas after extraction of lye was determined, and the results showed that the lye could completely absorb HF and SO2, while the absorption of SOF2 and SO2F2 was incomplete. In addition, in order to avoid clogging the lye pool with S generated in the presence of H2, we added a bag collector. In summary, we believe that H2 has a better effect on SF6 degradation than O2.

I. Introduction

The molecular structure of SF₆ is octahedral. The bond length ratio between sulfur and fluorine atoms in SF₆ is short and the bond energy is high. When the electric field is applied to sulfur hexafluoride, its molecules will be polarized, and with the increase of the electric field strength, the molecular polarization effect will become stronger and stronger, resulting in high insulation strength of sulfur hexafluoride. The electronegativity of sulfur hexafluoride gas is very strong, and it is easy to attract electrons to form negative ions, which makes sulfur hexafluoride gas has strong arc extinguishing performance. Sulfur hexafluoride is often used as an insulating material for high-voltage switches, high-capacity transformers, high-voltage cables, and gases [1]. The global warming potential of SF₆ gas is 23,500 times that of C02, which is a strong greenhouse gas. Due to its extremely stable chemical properties, SF₆ gas has a life span of 3,200 years, which is difficult to be decomposed in nature and is extremely harmful to the environment.