Brief description of the fine purification of the sulphur hexafluoride, and sulphur hexafluoride thus purified

摘要

is used as insulating and quenching medium in high voltage equipment and in the electronics industry, laser technology, medicine, x-ray technology, metallurgy etc. The process is universal in relation to the removal of most of the impurities present. Most can be removed reliably to a content of 1-100 ppm without great cost under conditions suitable for large scale operation. Very fine purificn. of SF6 from impurities is carried out by crystallisation at a rate of mixing of the interphase boundary of 1-50 mm/h and pref. at 222.3-217 K. The liq. phase concentrate of impurities obtd. is purified by sublimation at a pressure of 210 to 1.3-0.13 kPa. The SF6 is prepurified by distn. with 0.2-5% steam to remove the low boiling impurities. If it contains lower S fluorides and HF, the gas is prepurified by sorption on KOH, pt. of the impurities is subjected to catalytic decompsn. at 548-598 K, it is subjected to sorption on KOH and A1203 and then dried with type NaX zeolite zeolite. If the impure SF6 is obtd. from gas-filled high voltage equipment, pt. of the gas at high pressure is purified as above and the rest is passed through aq. alkali soln. at atmos. pressure, then dried on A1203 and type NaX zeolite.