High-temperature decomposition of SF6 gas and dry-fixation of the gaseous decomposition products

To develop a dry process of decomposition, fixation and resource-reconversion of SF6 gas, which has a global warming potential (GWP) of 23,900 times that of CO2, the high-temperature decomposition of SF6 gas without steam (the basic requirement for dry process fixation technology development) was examined. The gaseous decomposition products were further reacted with calcium carbonate and sodium bicarbonate, and the purity of the fluorides obtained was examined. It was found that 99% or more of the SF6 gas could be decomposed at or below temperatures of 1000degreesC by adding hydrogen gas. Furthermore, the decomposition reaction rate of SF6 gas could be evaluated with a first-order rate equation of SF6 gas concentration, and the apparent rate constant could be determined. In addition, the frequency factor (2.08x10(3) s(-1)) and the activation energy (8.314x10(4) J/mol) for decomposition of SF6 gas were calculated from an Arrhenius plot of the rate constants. It was also confirmed that the decomposition products HF and H2S could be separated and fixed by a gas-solid reaction with calcium carbonate or sodium bicarbonate, and the products formed were of sufficient purity for easy re-use (CaF2: 98% or more and NaF: 99% or more).