Decomposition mechanism of clean air based on ReaxFF molecular dynamics simulation and quantum chemical calculation

Abstract

SF6 is widely used in gas switchgear but has a strong greenhouse effect. The development of an environment-friendly switchgear that can replace SF6 is a current research hotspot. As a SF6 alternative technology, vacuum arc-extinguishing chamber plus clean air insulation has shown high application prospects. The clean air inside the switchgear decomposes under the effect of high temperature and discharge; however, only a few studies focused on its decomposition mechanism. In this work, the decomposition mechanism of clean air and the effect of temperature on the decomposition are simulated at the atomic level based on ReaxFF (Reactive force field) molecular dynamics and quantum chemistry theory. Results showed that the decomposition of clean air mainly generates NO, NO2, and N2O. NO is the main product at high temperatures and thus can be the characteristic decomposition product of clean air. The clean air has good self-recovery characteristics, and its decomposition can be substantially promoted by increasing the temperature. The decomposition rates of N2 and O2 under 3000 K can reach 7.00% and 8.00%, respectively, which are twice and four times those under 2000 K. These results can provide theoretical basis and engineering guidance for the development of environment-friendly switchgear with vacuum arc-extinguishing chamber plus clean air insulation.