Gas SF6 ko da kuma Sulfur Hexafluoride Gas Properties
Tarihin SF6
SF6 ko da sulfur hexafluoride na gas sunan abubuwan da aka kawo da adaduwa ce waɗanda suka haɗa shi don kuma sadarwa ta hanyar sulfur da kuma six fluorine. Wannan gas ta zama a shekarar 1900 a cikin makarantun Faculte de Pharmacie de, a Paris. A shekarar 1937, General Electrical Company ta bayyana cewa SF6 gas yana iya amfani a matsayin material mai inganta. Bayan Yakin Duniya na Biyu, ya'ni a tsakiyar shekara na 20th, tsohon fahimta kan amfani a matsayin material mai inganta a cikin gwamnatin kula yana saukarwa sosai. Allied Chemical Corporation da Pennsalt sun zama manyan industries na Amurka, wanda suka fara a yi aiki a matsayin gas na biro a shekarar 1948. A shekarar 1960, amfani a matsayin sulfur hexafluoride gas a cikin high voltage switchgear yana zama mafi girma. Saboda haka, babban mafi amfani a matsayin wannan gas, akwai masu aiki a Turai da Amurka wanda suka fara a yi aiki a matsayin gas na biro a lokacin. A farkon lokaci, SF6 gas an amfani kawai don inganta a cikin gwamnatin kula. Amma har zuwa an san cewa wannan gas yana da kyakkyawan inganta arc. Saboda haka, an fara a amfani a matsayin medium arc quenching a cikin circuit breaker. Duniya na farko SF6 gas insulated substation ta zama a Paris a shekarar 1966. Sulphur hexafluoride medium voltage circuit breakers ta fara a gada a cikin market daga shekarar 1971.
Amfani a Matsayin SF6 Gas
SF6 gas an yi a matsayin aiki a cikin reaction of fluorine (obtained by electrolysis) with sulfur.
A lokacin aiki na amfani a matsayin wannan gas, akwai wasu byproducts kamar SF4, SF2, S2F2, S2F10 suna fara a yi a matsayin small percentages. Ba kowane byproduct, impurities kamar air, moisture, and CO2 suna ci a cikin gas, a lokacin aiki. Duk waɗannan byproducts da impurities suna filter a matsayin stages of purification don samun pure and refined final product.
Abubuwan Kimiyya na SF6 Gas
Don baƙi abubuwan kimiyaya na properties of SF6 gas, za mu bincika structure of SF6 molecule. A cikin wannan gas molecule, daya sulfur atom yana da shi da six fluorine atoms.
Sulfur yana da atomic number of 16. Electronic configuration of sulphur atom is 2, 8, 6 i.e. 1S2 2S2 2P6 3S2 3P4. The fluorine atom has atomic number 9. The electronic configuration of fluorine is 1S2 2S2 2P5. Each sulphur atom in SF6 molecule creates a covalent bond with 6 fluorine atoms. In this way, sulfur atom gets total 6 covalent bonds, i.e. 6 pairs of electrons at its outer shell, and each fluorine atom gets 8 electrons in its outer most shell.
NB: – Here we can observe that, in sulfur hexafluoride external shell of sulphur atom has 12 electrons instead of 8 electrons. That means here sulfur does not obey general octal rule of atomic structure which states that, a stable atom requires 8 electrons at its outermost shell. This is not an exceptional case. Some elements in the 3rd period and below can form a compound that exceeds 8 electrons in its outer most shell. The molecular structure of this gas is shown below,
In this way, SF6 fully satisfies a stable structural condition. The effective radius of a sulfur hexafluoride molecule is 2.385 A. This electronic configuration and structure of this gas make SF6 extremely stable. The gas can be stable without any decomposition in its molecular structure up to 500oC. It is highly non-flammable. H2O and Cl cannot react with this gas. It also does not react with acid.
The SF6 gas is one of the heaviest gases. Density of this gas at 20oC at one atmospheric pressure, is about 6.139 kg/m3 which is about 5 times higher than air at same conditions. The molecular weight of this gas is 146.06. The variation of pressure with temperature is linear for sulfur hexafluoride and it is small within the service temperature, i.e. from – 25 to + 50oC. The volumetric specific heat of this gas is also high. It is around 3.7 times more than that of air, and that is why this gas also has a tremendous cooling effect in electrical equipment. The thermal conductivity of this gas is not very high it is even lower than air. Still it is quite suitable for cooling effect in circuit breaker. It is because, during dissociation of sulfur hexafluoride molecules around the electric arc, these molecules absorb a high amount of heat. This heat is then released when the molecules reform at the periphery of the arc. This process helps to transfer heat from a hot region to cool region very rapidly. That is why; this gas has an excellent cooling effect at high temperature although the thermal conductivity of SF6 is not very high.
Abubuwan Elektirik na SF6 Gas
SF6 gas is highly electronegative. Due to high electronegativity, it absorbs free electrons which are produced due to arcing between contacts of circuit breaker. Combination of free electrons with molecules produces heavy and big ions, which have very low mobility. Because of the absorption of free electrons and low mobility of ions SF6 has very excellent dielectric property. The dielectric strength of SF6 gas is about 2.5 times more than that of air.
