Sf6 by-products: safety, cleaning, and disposal concerns

SF By-products: Safety, Cleaning,
and Disposal Concerns
U.S. EPA’s International Conference on SF6
and the Environment
November 29, 2006
San Antonio, TX
Slow reacting with a relatively high molecular weight and extremely stable molecular structure. Excellent insulation properties, strong arc quenching abilities, and high dielectric strength Under high temperature conditions (> 350° F), SF decomposes into products that are toxic Reactive decomposition byproducts form when SF is exposed to: Decomposition byproducts can take the form of gas or powders Other types of contaminants can include moisture and air (from handling or leakage), dust and particles (mechanical generation) Disulfur Decafluoride (sulfur pentafluoride) • Irritating to the eyes, nose, and throat, pulmonary edema and other lung damage, skin and eye burns, nasal congestion, bronchitis; powders may cause rashes – strong irritating “rotten egg” odor at low – Eyes, nose, throat and lung irritation at high – Presence of white, gray, or tan powders toxic to cell cultures than other byproducts 0.025 ppm*
*Revised in 1989 to a PEL-ceiling value of 0.01 ppm; enforcement of the new limit
stayed by OSHA, until available sampling and analytical technique is published a 6
Degree of Contamination Risk
Cylinders
Non-arced
Normally Arced
Heavily Arced
– Work in well-ventilated areas– No smoking, refrain from welding, avoid open flame • Intermediate Risk (normally arced SF ) – Use of personal protective equipment (i.e., respiratory device, protective clothing such as rubber gloves, footwear, goggles) for removal/handling of solid SF6 – Ventilate and test enclosed areas for adequate O2 • Provide personnel with written instructions for safe handling of SF -filled equipment, – Procedures for low, intermediate, and high • Train personnel on cleaning procedures – Removal of powdery deposits with vacuum cleaner – Removal of disposable protective equipment and waste bags into a properly labeled hazardous waste drum – Onsite purification unit for acceptable levels – Off-site reclamation methods for non-acceptable • Handle gas that results as non-reusable decomposition products to below 200 ppmv for transport • 50 ppmv - maximum tolerable impurity level for • 12 ppmv if the sum concentration of SO and • Gas chromatograph (not suitable for field • Generally need to store and transport – disposal of non-reusable gas– off-site purification – Clearly label cylinder as used gas (Apply danger labels and/or use a different color) – Follow local transport regulations– Arrange for disposal of waste that complies Source: Bessede, Huet, Montillet - AREVA T&D • Incineration plants offer destruction • SF gas can be destroyed at a thermal – Dissociates into reaction products that are passed through wet scrubbers to form gypsum, fluospar minerals – Fluorospar CAF used as an additive in – Byproducts of SF6 Use in the Electric Power – Service Provider Directory– Catalog of Guidelines and Standards for the

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