An Investigation of Harmless Treatment of SF6 Adsorbent for Gas Insulated Equipment

SF₆ gas insulated equipment represented by gas insulated switchgear (GIS) has been widely applied in 110 kV and above substations, due to its advantages of small occupation of land, compact structure and high reliability. The service life of the early SF₆ insulated equipment exceeded 20 years, most of them has entered the maintenance period or is directly facing retirement; in this process, a large number of SF₆ adsorbents would be retired. The SF₆ adsorbent in the SF₆ gas insulated equipment will adsorb a large amount of toxic SF₆ decomposition products during the service, and it could be great harm to the environment without harmless treatment. In order to solve this problem, this paper analyzed the adsorption components of the ex-service SF₆ adsorbent for gas insulated equipment. On this basis, the environmental-friendly processing method of the SF₆ adsorbent for gas insulated equipment was studied: the main decomposition products of SF₆, namely, SOF2, SO₂F₂ and HF, adsorbed in SF₆ adsorbent are toxic acid fluoride sulfide, and they can neutralize with calcium hydroxide to generate calcium fluoride precipitate which is difficult to be ionized and release toxic and harmful fluorine-containing ions to the environment. The adsorption components of ex-service adsorbent and the influence of amounts of calcium hydroxide, reaction time and reaction temperature on the harmless treatment of adsorbents were studied via thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). In addition, the harmless treatment effect of the SF₆ adsorbent for gas insulated equipment were verified via boiling. And the following experimental results were obtained. Firstly, SF₆ adsorbent for the SF₆ gas insulated equipment would adsorb abundant water and SF₆ decomposition products, that is, SOF₂, SO₂, SO₂F₂, SOF₄, SF₄ and HF, etc during the service period. Secondly, the best harmless treatment effect of SF₆ adsorbent could be achieved under the condition that Ca(OH)₂ with a weight of 20% treated adsorbent for 1 h.