Seven, hexafluoride application
Sulfur hexafluoride is a colorless, odorless, non-toxic, non-combustible inert gas having a molecular weight of 146.07 and a density of 6.1 kg/m3 at 20 ° C and 0.1 MPa, which is about 5 times the density of air. Sulfur hexafluoride is gaseous at normal temperature and pressure, its critical temperature is 45.6 ° C, the triple point temperature is -50.8 ° C, and the sublimation point temperature is -63.8 ° C under normal pressure. The molecular structure of sulfur hexafluoride is octahedral, the bonding distance is small, and the bonding energy is high, so its stability is very high. When the temperature does not exceed 180 °C, its compatibility with electrical structural materials is similar to that of nitrogen. Carbon dioxide is heavier than air and does not support combustion. Many fire extinguishers therefore use carbon dioxide to extinguish fires. The carbon dioxide fire extinguisher directly uses liquefied carbon dioxide to extinguish the fire. In addition to the above characteristics, there is an advantage that the solid residue is not left after the fire is extinguished.
Chemically stable. Slightly soluble in water, alcohol and ether, soluble in potassium hydroxide. Does not react chemically with sodium hydroxide, liquid ammonia and hydrochloric acid. It does not react with copper, silver, iron or aluminum in a dry environment below 300 °C. Below 500 ° C does not work for quartz. It reacts with sodium metal at 250 ° C and reacts in liquid ammonia at -64 ° C. It is decomposed by heating with hydrogen sulfide. At 200 ° C, in the presence of specific metals such as steel and silicon steel, it can promote its slow decomposition.
1. A new generation of ultra-high voltage dielectric materials. As a good gas insulator, it is widely used for gas insulation of electronic and electrical equipment. Electronic grade high purity sulfur hexafluoride is an ideal electronic etchant widely used in the field of microelectronics technology, and is used as a plasma etching and cleaning agent in the manufacture of large integrated circuits such as computer chips and liquid crystal screens. Used as a fluorine source for the production of fluorine-doped glass in the preparation of optical fibers, as a dopant for the isolation layer in the manufacture of low-loss, high-quality single-mode fibers. It can also be used as an admixture gas for nitrogen excimer lasers. Used as a tracer, standard gas or standard mixture in meteorological, environmental testing and other sectors. Used as an arc extinguishing and bulk transformer insulation material in high voltage switches. It can also be used in particle accelerators and arresters. It is used as a refrigerant in the refrigeration industry due to its good chemical stability and non-corrosion to equipment (operating temperature -45~0 °C). It is also used for radiochemistry due to its high stopping ability for alpha particles. In addition, it acts as a counter-adsorbent to displace oxygen from mine coal dust.
2. It can be used in the smelting and casting process of non-ferrous metals, and can also be used for degassing and purification of molten aluminum and its alloys. In the microelectronics industry, sulphur hexafluoride can be used to etch silicon surfaces and remove organic or inorganic films on semiconductor materials, and can act as a single film fiber barrier dopant during the fabrication of optical fibers. The current interrupter with sulphur hexafluoride has a high rated voltage and is not easy to burn. In addition, sulfur hexafluoride is also used as an insulating medium for various accelerators, ultra-high voltage electrical storage devices, coaxial cables and microwave transmission. At present, sulfur hexafluoride is a widely used tracer for measuring atmospheric pollution, and the trace distance can reach 100km. Sulfur hexafluoride has good chemical stability and does not corrode equipment. It can be used as a refrigerant in the refrigeration industry (operating temperature is between -45 and 0 °C). It is used as a refrigerant instead of Freon. It has no destructive effect on the ozone layer and is environmentally friendly. And the performance requirements are a promising refrigerant. A tracer for determining the degree of atmospheric pollution used as an electrical insulating medium and an arc extinguishing agent.
3. Mainly used for arc extinguishing in high voltage switch, used as insulation material in large capacity transformer and high voltage cable. It can be used as a gas insulating material in nuclear particle accelerators and lightning arrester X-ray equipment. It has good chemical stability with SF6 and does not corrode equipment. It can be used as a refrigerant in the refrigeration industry (operating temperature is between -45 and 0 °C). SF6 has a high stopping ability for α-particles, so it is also used in radiochemistry; it can also be used as a anti-adsorbent to displace oxygen from mine coal dust.
4. Used as a gas insulator for electronic equipment and radar waveguides.
Eight, matters needing attention
Inhalation: Remove quickly from the scene to fresh air. Keep the airway open. If breathing is difficult, give oxygen. If breathing stops, take artificial respiration immediately and seek medical attention.
Hazardous characteristics: In case of high heat, the pressure inside the container increases, there is a danger of cracking and explosion.
Hazardous combustion products: sulfur oxides, hydrogen fluoride.
Fire fighting method: This product is not flammable. Cut off the air supply. Spray the water to cool the container and, if possible, move the container from the fire to the open space.
Leakage emergency treatment
Emergency treatment: quickly evacuate people from the contaminated area to the upper reaches, and isolate them, strictly restrict access. It is recommended that emergency personnel wear self-contained positive pressure breathing apparatus and wear general working clothes. Cut off the source of the leak as much as possible. Proper ventilation and accelerated diffusion. Use it whenever possible. The leaking container should be properly disposed of, repaired, and used after inspection.
Packing method: steel gas cylinder
Precautions for transportation: When transporting by rail, it must be certified by biological test and checked according to the certificate of conformity. The helmet on the cylinder must be worn when transporting in a rigid bottle. The cylinders should be placed flat and the bottles should be in the same direction. They should not cross; the height should not exceed the fence of the vehicle and be secured with triangular wooden mats to prevent rolling. It is strictly forbidden to mix and transport with combustibles or combustibles, oxidants, etc. Summer should be transported in the morning and evening to prevent sun exposure. It is forbidden to slip when transporting by rail.
Although sulphur hexafluoride itself is non-toxic and harmless to the human body, it is a greenhouse effect gas. Its single-molecule greenhouse effect is 22,000 times that of carbon dioxide. It is the six greenhouses banned in the Kyoto Protocol. One of the gases.
According to the GWP (Global Warming Potential) index of many greenhouse gases proposed by the IPCC, sulfur hexafluoride has the largest GWP value, and the GWP value of 500 years is 32,400. Due to the high chemical stability of sulfur hexafluoride, it is in the atmosphere. The retention time can be as long as 3,200 years.
In today's world, the emission of sulphur hexafluoride is very small, and the contribution to the greenhouse effect is completely negligible compared to carbon dioxide. However, for the long-term environmental protection and safety considerations, how to properly and properly recover and purify sulphur hexafluoride gas, It is a problem that must be solved.