The History of SF6 and the Importance of Proper Handling of Used Gas
The Role of SF6 in the Energy Industry
Sulfur Hexafluoride (SF6) has been widely used as an insulating and arc-quenching gas in medium-voltage (MV) and high-voltage (HV) gas-insulated switchgear (GIS). The use of SF6 as an insulating medium dates back to the 1930s, but it became commercially significant in the 1960s, primarily in HV applications. Over time, its adoption extended to the MV sector, making SF6-based GIS a standard component of power infrastructure worldwide.
Its popularity stems from its excellent electrical insulating properties, non-flammability, non-toxicity, and thermal stability. SF6 remains chemically stable up to 500°C, does not corrode equipment, and has a low decomposition rate after arcing, making it a superior choice compared to alternatives like air-insulated switchgear (AIS) or solid-insulated switchgear (SIS). GIS benefits from these properties by requiring less maintenance, having a compact design, and offering high reliability.
However, despite these advantages, SF6 is a major greenhouse gas (GHG), with a global warming potential (GWP) 23,500 times greater than CO₂, as identified under the Kyoto Protocol. Increasing regulatory pressure worldwide is pushing for its phase-out in the near future.
With GIS units installed in the 1980s and 1990s reaching the end of their operational life, concerns arise about how to manage used SF6. Additionally, once regulatory bans take effect, handling existing SF6 inventories will become a pressing issue. Below, we explore the available options for dealing with used SF6.
[caption id="attachment_4455" align="aligncenter" width="527"]
SF6 GAS[/caption]
Managing Used SF6: Available Options
Currently, switchgear users—including utilities and industrial operators—have three main options for handling used SF6:
- Off-Site Reconditioning
- Off-Site Destruction
- On-Site Recycling
1. Off-Site Reconditioning
Process Overview
Reconditioning involves extracting used SF6 and transporting it to a specialized facility for filtration and purification. The process removes contaminants such as oil, moisture, and by-products through cryogenic liquefaction. The purified SF6 is then reintegrated with virgin SF6, ensuring high-quality gas for reuse.
The cryogenic process follows these steps:
- The SF6 container’s pressure is increased to over 700 psi (48.3 bar).
- The temperature is gradually lowered from -20°C to -40°C, liquefying SF6 while other gases (e.g., nitrogen, oxygen) remain in vapor form.
- The unwanted gases are separated and released, leaving behind purified SF6.
Pros of Reconditioning
- Reduces environmental impact compared to destruction, as it minimizes SF6 emissions.
- Avoids the need for on-site recycling equipment and personnel training.
- Allows users to mitigate emissions liability.
Cons of Reconditioning
- Users depend on third-party services, which can be costly.
2. Off-Site Destruction
Process Overview
This method involves collecting SF₆ from switchgear and transporting it to a facility where it is completely destroyed under high temperatures.
Pros of Destruction
- Helps reduce SF₆ inventories.
- Lowers emissions liability for switchgear users.
Cons of Destruction
- Releases high levels of emissions during the destruction process.
- No reliable research quantifies these emissions accurately.
- The process is costly and requires third-party involvement.
3. On-Site Recycling
Process Overview
This method is similar to reconditioning but is conducted by the user on-site using filtration systems. It removes contaminants but does not enhance the gas’s purity to the same extent as reconditioning.
Pros of Recycling
- Users maintain full control over their SF₆ inventory.
- Eliminates the need for external transport or reliance on third-party services.
Cons of Recycling
- Requires investment in filtration equipment and personnel training.
- Does not significantly improve SF₆ purity, limiting its reuse potential.
Future of SF₆ Inventories After Phase-Out
As regulatory restrictions increase, the industry faces uncertainty regarding the fate of existing SF₆ inventories. With no alternative applications for SF₆ beyond switchgear, both reconditioning and recycling will become obsolete. Meanwhile, destruction remains expensive and environmentally problematic due to its high emissions.
Unless a more efficient and eco-friendly destruction method is developed, industries and policymakers will need to find a viable solution for removing SF₆ from circulation in a sustainable manner.
Additional Considerations
Why Do Some Users Prefer Virgin SF₆?
- High-quality SF₆ is required for GIS applications, and reconditioned or recycled SF₆ may not meet strict purity standards.
- Some users have had negative experiences with improperly reconditioned SF₆.
- Certain switchgear manufacturers prohibit the use of reconditioned SF₆ in their products, voiding warranties if used.
Environmental Impact of Virgin SF₆ Production
Producing virgin SF₆ results in significantly higher emissions compared to reconditioned gas. For instance, manufacturing a new SF₆ cylinder (45.5 kg) emits 1.5 to 3.6 kg of SF₆, whereas a reconditioned cylinder emits only 0.29 kg. Moreover, surplus production often leads to excess SF₆ being stored unnecessarily.
Conclusion
As SF₆ usage faces increasing regulatory pressure, users must consider their available options for handling existing SF₆ inventories. Depending on operational needs, they can opt for reconditioning, destruction, or recycling. However, a long-term sustainable solution for phasing out SF₆ without causing significant environmental harm remains elusive. Finding a balance between cost, efficiency, and environmental responsibility will be crucial in the coming years.
Professiona Switchgear supplier and manufacturer
- Zhejiang GONGSHUN Electrical Co.,Ltd (electricgs.com), Our company was founded in the late 1990s, specializing in the production of inflatable cabinets, SF6 inflatable cabinets, and various high and low voltage complete sets of electrical equipment. It has multiple subsidiaries under its jurisdiction, including high-voltage load switch branch, high-voltage circuit breaker branch, high-voltage fuse branch, and technology development branch.Our technical expertise, comprehensive product portfolio and long-term rich experience are helping many customers in need to solve their power problems. We’re happy to help at any time. Whether you need application product advice or technical assistance, our global service team is committed to providing you with the right support. For more technical information about medium voltage earthing switch, feel free to contact us, send an email to gongshun@electric-cn.com
- Our company specializes in producing 12KV-40.5KV series high-voltage electrical products: FZN58, FLN48, FLN36, FZRN25, FZN21, FN18, ZFN16, FN12, FN8, FN7, FN5, XRNT, XRNP, VS1, ZN28, ZW8, ZW32, JN15, GN19, GN22, GN24, GN30, CLXGN15-12, HXGN □ -12, DXG-12 (L), DFW □ -12 high-voltage cable branch box, CLXGN □ -12 (SF6) series inflatable cabinet 12KV and 35KV cable accessories, etc; CLVXP-12 indoor AC high voltage fixed switchgear, CL-SIS-12 compact solid insulated ring main unit, professional assembly Schneider SC6 (SF6) series load switchgear, ABB produced SFG (SF6) series load switchgear and other series products; Distribution and agency of high-voltage load switches and inflatable cabinets produced by Schneider Electric and ABB; Siemens produces the 3AJ1 series of indoor medium voltage vacuum circuit breakers and other related products. The company has a complete range of products and has been operating safely on domestic and international power grids for a long time, receiving unanimous praise from both new and old users. Among them, multiple products such as FZRN25, FN12, FLN36-12, XRNT-12 have been exported to various countries and regions in East Asia, South Asia, Southeast Asia, Africa, and the United States.
