Study on the Compatibility of Gas Adsorbents Used in a New Insulating Gas Mixture C 4 F 7 N/CO 2

摘要

An environment-friendly insulating gas, perfluoroisobutyronitrile (C 4 F 7 N), has been developed recent years. Due to its relatively high liquefaction temperature (around ?4.7 °C), buffer gases, such as CO 2 and N 2 , are usually mixed with C 4 F 7 N to increase the pressure of the filled insulating medium. During these processes, the insulating gases may be contaminated with micro-water, and the mixture of H 2 O with C 4 F 7 N could produce HF under breakdown voltage condition, which is harmful to the gas insulated electricity transfer equipment. Therefore, removal of H 2 O and HF in situ from the gas insulated electricity transfer equipment is significant to its operation security. The adsorbents with the ability to remove H 2 O but without obvious C 4 F 7 N/CO 2 adsorption capacity are essential to be used in this system. In this work, a series of industrial adsorbents and desiccants were tested for their compatibility with C 4 F 7 N/CO 2 . Pulse adsorption tests were conducted to evaluate the adsorption performance of these adsorbents and desiccants on C 4 F 7 N and CO 2 . The 5A molecular sieve showed high adsorption of C 4 F 7 N (22.82 mL/g) and CO 2 (43.86 mL/g); F-03 did not show adsorption capacity with C 4 F 7 N, however, it adsorbed CO 2 (26.2 mL/g) clearly. Some other HF adsorbents, including NaF, CaF 2 , MgF 2 , Al(OH) 3 , and some desiccants including CaCl 2 , Na 2 SO 4 , MgSO 4 were tested for their compatibility with C 4 F 7 N and CO 2 , and they showed negligible adsorption capacity on C 4 F 7 N and CO 2 . The results suggested that these adsorbents used in the gas insulated electricity transfer equipment filled with SF 6 (mainly 5A and F-03 molecular sieves) are not suitable anymore. The results of this work suggest that it is a good strategy to use a mixture of desiccants and HF adsorbents as new adsorbents in the equipment filled with C 4 F 7 N/CO 2 .