Potential Hazards Relating to Pyrolysis of c-C{sub 4}F{sub 8}O, n-C{sub 4}F{sub 10}, and c-C{sub 4}F{sub 8} in Selected Gaseous Diffusion Plant Operations

Trowbridge, L.D.

doi:10.2172/814073

Cited by 2 publications

(1 citation statement)

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“…Second, the primary alternative gas has a mole fraction of less than 20% in order to simultaneously lower the GWP significantly compared to SF 6 and satisfy liquefaction requirements. Because SF 6 in the existing 24 kV MV-GIS products is maintained at a pressure of 1.3 bars, we verified that the liquefaction requirements are satisfied in the pressure range 1.0-2.0 bar, for the gas mixture containing a maximum of 20% mole fraction of C 4 F 7 N. Third, significant amounts of toxic carbon monoxide (CO) and trace amounts of extremely toxic perfluoroisobutylene (PFIB) have been observed during the anaerobic thermal decomposition of F-gases in high-temperature applications [4]. To ameliorate these concerns, oxygen (O 2 ) must be considered in the gas mixture.…”

Section: Previous Workmentioning

confidence: 64%

Transport and radiation properties of C₄F₇N-CO₂ gas mixtures with added oxygen

Narayanan¹,

Gnybida²,

Rümpler

2022

J. Phys. D: Appl. Phys.

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Owing to global and local legislative mandates pertaining to greenhouse gas emission reduction targets, the focus of industries dealing with electrical power management has shifted towards SF6 replacement within electrical or electromechanical equipment since 2010. In particular, fluoronitrile- (C4F7N) or fluoroketone- (C5F10O) based gas mixtures have been identified as the most promising candidates for this purpose in both medium-voltage (MV) and high-voltage (HV) gas insulated switchgear (GIS). The temperature and pressure ranges of interest are 300 K-30 kK and 1-5 bars respectively, which are relevant to the short-circuit current arcing conditions within an MV-GIS. In this work, we focus on a gas mixture with a fluoronitrile mole fraction lower than 20%, with or without O2 having a mole fraction lower than 20% and the rest of the mixture was carbon dioxide (CO2). Throughout this work, we validate our calculation results with published data for 10% and 20% C4F7N-CO2 mixtures at 1 bar and 5 bars and hint at the possible sources of discrepancies. Our local thermodynamic equilibrium (LTE) based chemical composition results indicate that the addition of 20% O2 to C4F7N-CO2 mixtures significantly reduced CO formation while increasing COF2 formation. However, the addition of 20% O2 induced marginal modifications to the thermodynamic, transport and radiation properties of 10% and 20% C4F7N-CO2 mixtures. Finally, after utilizing the properties database to calculate steady-state temperature proles for a low-current (10 A) free-burning arc without metallic vapor, we demonstrate that the arc columns of 10% and 20% C4F7N-CO2 mixtures with or without O2 are less diffuse compared to air but more diffuse compared to SF6. We explain the order of diffuse-to-constricted proles and arc interruption capabilities for different gases in terms of their thermal conductivities and diffusivities.

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Section: Previous Workmentioning

confidence: 64%