The Degradation Of Potent Greenhouse Gas Sulfur Hexafluoride （SF₆） By Stainless Steel Slag

With the rapid development of world economy and the accelerated process ofindustrialization, global warming has become one of the world’s top tenenvironmental issues. One of the six greenhouse gases, sulfur hexafluoride （SF₆） asthe provisions of the Kyoto Protocol, the atmospheric lifetime is3,200years, and100years of global warming potential is22,800times than that of carbon dioxide（CO₂）. So sulfur hexafluoride is one of strong greenhouse gases. In the present, theannual emissions of SF₆gas into the atmosphere is equivalent to125million tons ofCO₂gas, which has become an important goal of reducing greenhouse gas emissions.SF₆destruction process will emit some high-reactive, corrosive and toxicdecomposition byproducts, such as the S2F10, SF₄and HF. Therefore, emissionreduction of SF₆is very urgent.Based on the scientific foundation of SF₆effective degradatation by stainlesssteel slag, this paper investigated the feasibility of SF₆by stainless steel slag and theinfluence of SF₆degradation process under different reaction conditions. The resultsshowed that stainless steel slag could effectively remove SF₆. Higher removalefficiency and more degradation were obtained with smaller particle size of thestainless steel slag and higher reaction temperature. With the reaction temperature of700oC, SF₆initial concentration of2.0%and gas flow of13.4ml/min, the largestdegradation of78.5mg/g was obtained by stainless steel slag （＜100mesh）.The degradation process of SF₆was studied in the stainless steel powder, ironoxide and calcium oxide. The amount of SF₆degradation by stainless steel powder at500oC,600oC and700oC, were4.7,5.2and6.7times than that of stainless steel slag,respectively. The amount of SF₆degradation by iron oxide in the three temperaturewere83%,108%and166%more than that by stainless steel slag, respectively. ButSF₆degradation by calcium oxide was poorer. These results also confirmed that theiron oxide, calcium oxide and a small amount of Fe, Cr and Ni in the stainless steel slag could degradate SF₆effectively.The products of the degradation process were analyzed. The results showed thatthe products in gas phase were soluble in water,mainly including SOF2, SO₂F2, SO₂and SO₃, which infered by the main components of absorption liquid. The productsin solid phase were metal fluorides. According to the ion concentration in absorptionliquid and solid products, the dominant reaction of stainless steel slag and sulfurhexafluoride was supposed to be4Fe₂O₃+6SF₆=8FeF3+6SOF2+3O₂.Based on the concept of "waste treatment by waste", this paper used stainlesssteel slag to degradate SF₆for the first time. This paper provided a new method forthe degradation of sulfur hexafluoride and achieved the purpose of recycle ofstainless steel slag.