专注于SF6气体检测的专业化
What are the reasons for the impure effect of sulfur hexafluoride gas?
If the purity of sulfur hexafluoride gas is low, its insulation strength will be greatly reduced, and it is easy to be broken down by high voltage when used in electrical insulation, resulting in accidents from the test and research results of relevant departments. So what are the reasons for the impurity of sulfur hexafluoride gas?
(1) Sulfur hexafluoride gas is not pure, and contains highly toxic low sulfur fluoride, hydrogen fluoride and other toxic gases at the factory. At present, the method of producing sulfur hexafluoride gas in 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%. Its composition has sulfur fluorine compounds, such as: S2, F2, SF2, SF4 and so on; Sulfur fluoride compounds such as SOF2, SO2F2, SOF4, 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 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 products with a purity of more than 99.8%. 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 sulfur hexafluoride, the International Electrotechnical Commission (IEC) and many countries have formulated quality standards for sulfur hexafluoride, 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, the decomposition of SF6 gas in the arc and the reaction with oxygen: toxic substances such as thionyl fluoride, sulfuryl tetrafluoride and sulfuryl fluoride will be generated.
(3) The sulfur hexafluoride gas decomposition in the electrical equipment reacts chemically with the water in it to produce certain toxic products. For example, the secondary reaction of SF6 gas decomposition with water produces hydrofluoric acid, sulfur dioxide, sulfuric acid, etc.
(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: ALF3 (solid powder) ALF3 (solid powder) CuF2(solid powder) and other solid powders.
(5) SF6 gas and decomposition in electrical equipment react with insulating materials to produce some toxic products. Such as insulating parts with epoxy phenolic glass cloth plate (rod, tube) containing silicon components; Or epoxy resin castable parts, moulded parts and porcelain bottles, silicone rubber, silicone grease with quartz sand and glass as fillers play a chemical role to generate SiF4, Si (CH3) 2F2 and other products.
These products of high temperature decomposition of sulfur hexafluoride gas will lead to the problem of impurity of sulfur hexafluoride gas. In the purchase of the first to avoid, find a regular manufacturer to buy, and accompanied by product testing reports.