Preparation Of Fe-based Composites And Their Thermal Degradation Properties Of SF₆

Since the 20^th century,countries around the world have been developing technology and economy at an unprecedented speed,which causes prominent environmental problems and resource scarcity.Among them,global warming caused by the greenhouse effect is one of its typical problems.Sulfur hexafluoride(SF₆),as one of the main greenhouse gases under the Kyoto Protocol,can remain in the atmosphere for up to 3200 years,and its global warming potential(GWP)is approximately 23,900 times than that of the same amount of CO₂.Nowadays,SF₆,as an insulating arc extinguishing gas that must be used in HV,EHV and UHV electrical appliances,is one of the very important materials in the field of high-voltage power transmission and transformation and electrical appliances manufacturing in China.According to relevant statistics,about 8,100 tons of SF₆(from the power industry)are emitted every year in the world,which is equivalent to 200 million tons of carbon dioxide equivalent(Mt CO₂e).Therefore,studying the safe emission reduction of SF₆ is an urgent problem.Based on the scientific basis that metals and metal oxides can achieve SF₆degradation,this paper investigates the thermal degradation effects of some metals and metal oxide-based composite materials on SF₆ regarding some of the current problems in SF₆ degradation.The specific content is as follows:1.A series of Fe-based mixed materials with different supports were prepared by the simple physical mixing method,and the mixed materials were used as degradation agent to be filled into the reaction bed for thermal degradation experiments.We found that under certain conditions,the degradation of SF₆ within a certain period of time was achieved.Among them,the Fe OOH-SiC can completely degrade SF₆ for 200 min at600?.In addition,it successfully achieved the degradation of SF₆ in the atmospheric environment.It was observed by GC that only SO₂,CO₂,Si F₄ and a small amount of HF and other gases that can be completely absorbed by the Na OH solution were produced during this degradation process,and no toxic and severely corrosive gases such as SOF₄,SO₂F₂ and SF₄ etc were involved.2.With SiC as the carrier and Fe OOH as the supporting,it was found that Fe OOH was successfully and uniformly supported on SiC through various characterizations,and the degradation effect of various ratios of SiC-Fe OOH composite materials on SF₆was studied.We found that SiC-Fe OOH materials have higher activity for SF₆degradation.The higher the ratio of Fe OOH,the higher the reaction temperature,the more the mass of SiC-Fe OOH and the slower the flow rate,the longer the time for SF₆to be completely converted with great degradation efficiency.Under certain conditions,the SF₆ removal rate remained 100%within 260 min.In addition,under the initial concentration of 35%SF₆,using SiC-Fe OOH to degrade SF₆,complete degradation could still be achieved within 140 minutes.At the same time,the phase characterization of each substance before and after the reaction was studied,and the effluent gas after the reaction was detected by FTIR.No severe corrosive gas was produced during the whole process.Finally,the mechanism of effective degradation for SF₆ in the whole reaction process was proposed based on these characterizations.