Immobilization of By-products of Sulfur Hexafluoride (SF6) Decomposition in the Presence of Bead-Type Calcium Oxide (CaO) Using High-Temperature Kiln Furnace

Abstract

The cement industry is a typical energy-intensive industry that emits massive greenhouse gases during decarboxylation and calcination with high energy consumption per unit of value-added production. As a result, the pressure for mandatory reduction of cement production increases, which leads to a considerable economic loss. Since the marginal cost of greenhouse gas reduction is high, it is necessary to apply the development of economical greenhouse gas reduction measures and technologies. Sulfur hexafluoride (SF₆) is a greenhouse gas with a very high global warming potential, it is mainly used for insulating materials and semiconductors for electric power and transmission facilities with heavy electric fields. This study aims to decompose SF₆ gas which gets discarded after being used as an insulator for heavy electric devices in high temperatures by fixating it into free calcium oxide (CaO) in cement kilns and using it as a supplementary material like fluorspar and plaster. Based on results from previous research, in this study the discarded SF⁶ was fixated it into the bead type of CaO under a fixation temperature of 1000℃. The fixation rate calculated using the concentration difference between the front end and the hinder end of the decomposed by-products was 95% on average. The bead type of the fixated by-product was largely composed of calcium fluoride, anhydrite, and portlandite as the main composition minerals. Therefore, it is considered that if sulphur hexafluoride can be decomposed in high temperatures and fixated into free CaO in cement kilns, it can be used as supplementary minerals like fluorspar and plaster.