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SF6安全保障专家
专注于SF6气体检测的专业化
What are the hazards and prevention of sulfur hexafluoride (SF6) gas?
发布时间：2017-05-19
来源：ydlcb 浏览次数：37次
Sulfur hexafluoride (SF6) gas is one of the six greenhouse gases found today. A large amount of SF6 gas is used in the high-voltage electrical appliance manufacturing industry. Due to improper use, management or failure to recover and regenerate it in a correct way, SF6 gas and the toxic decomposition produced under the action of high-temperature arc are discharged into the atmosphere, which brings pollution and destruction to the environment on which human beings depend. At the same time, it will adversely affect the normal operation of electrical equipment and people's health.
(1) SF6 products are not pure, and contain highly toxic low sulfur fluoride, hydrogen fluoride and other toxic gases when leaving the factory. As we all know, the current method of manufacturing SF6 gas in the chemical industry is mainly the direct combination reaction of elemental sulfur and excessive gaseous fluorine; That is S+3F2→SF6+Q (giving off heat). The composition and content of the impurities vary greatly due to the purity of the raw materials, the material of the production equipment, the process conditions and other factors, and the total content of impurities can reach 5%. It consists of sulfur fluorine compounds, such as: S2, F2, SF2, SF4, S2F10O, etc. Sulfur fluoro compounds such as SOF2, SO2F2, SOF4, S2F10O, etc., and impurities brought into the raw materials such as HF, OF2, CF4, N2, O2, etc. In order to purify impurities in the crude product, the synthesized SF6 gas body also needs to go through a series of purification processes such as washing, alkali washing, pyrolysis (removal of highly toxic decafluorides), drying, adsorption, freezing, distillation and purification to obtain a purity of more than 99.8% of the product. Then it is pressurized with a compressor and filled into a cylinder cooled to -80 ° C left and right, which exists in liquid form. When in use, the decompression is released and the gas is rushed into the electrical equipment.
In addition to the impurities produced in the above synthesis process, in addition, in the gas filling process may also be mixed with a small amount of air, water, and mineral oil and other impurities, these impurities are with or will produce certain toxic substances. Therefore, in order to ensure the purity and quality of SF6 products, the International Electrotechnical Commission (IEC) and many countries have formulated quality standards for the factory SF6 products, and require manufacturers to provide biological test non-toxic certificates when supplying.
(2) The SF6 gas in the electrical equipment produces some toxic products when the high-temperature arc occurs.
For example, decomposition of SF6 gas in an arc and reaction with oxygen:
2SF6 + O2 →2SOF2 + 8F (thionyl fluoride)
2SF6 + O2 →2SOF4 + 4F (sulfuryl tetrafluoride)
SF6 →SF4 + 2F (sulfuryl tetrafluoride) SF6 →S + 6F (sulfur)
2SOF4 + O2 →2SO2F2 + 4F (sulfuryl fluoride)
(3) The SF6 gas decomposition in the electrical equipment reacts chemically with the water in it to produce some toxic products. For example, secondary reactions of SF6 gas decomposition with water: SF4 + H2O →SOF2 + 2HF (hydrofluoric acid) SOF4 + H2O →SO2F2 + 2HF (hydrofluoric acid) SOF2 + H2O SO2F2 + 2H2O →SO2 + 2HF (sulfur dioxide) → H2SO4 + 2HF (sulfuric acid)
(4) SF6 gas and decomposition in electrical equipment react with electrodes (CU-W alloy) and metal materials (AL, Cu) to produce some toxic products. For example, SF6 gas and decomposition react with electrodes or other materials: 3SF6 + W → WF6 (gaseous) + 3SF4
3F + AL →ALF3 (solid powder) 3SOF2 + AL2O3 →2ALF3 (solid powder) + 3SO2
SF6 + Cu →CuF2(solid powder) + SF6 4SF6 + W + Cu →2S2F2 (gas) +3WF6 (gas) + CuF2(solid powder)
(5) SF6 gas and decomposition in electrical equipment react with insulating materials to produce some toxic products. Such as epoxy phenolic glass fiber cloth plate (rod, tube) and other insulating parts containing silicon; Or epoxy resin castable parts, molded parts and porcelain bottles, silicone rubber, silicone grease with quartz sand and glass as fillers play a chemical role to produce SiF4, Si (CH3) 2F2 and other products.