In the demanding environment of gas chemical plants, high-performance butterfly valves play a vital role in ensuring safe and efficient operations. These valves are engineered to handle extreme conditions, including high pressure, corrosive gases, high temperatures, and flammable media, while maintaining strict sealing requirements. This article delves into the specific applications and technical essentials of these crucial components.
Key Applications:
- Syngas Regulation and Transmission:
- Handling syngas (H₂, CO, CO₂, H₂S) at 200-400℃ and 2.5-8.0 MPa requires robust valves.
- Metal hard-seal butterfly valves (e.g., Inconel 625 body) with flexible graphite seals provide high-temperature and high-pressure resistance, meeting API 598 Class VI leakage standards.
- Coatings like Hastelloy C276 on valve plates combat H₂S corrosion, preventing stress corrosion cracking.
- Acid Gas Treatment (CO₂, H₂S Removal):
- In amine liquid (MDEA) absorption tower lines, valves must withstand acid gases and chemical solvents.
- PFA-lined butterfly valves offer chemical corrosion resistance, while duplex stainless steel (2205) is suitable for wet CO₂ environments with Cl⁻.
- Oxygen and Inert Gas Transmission:
- Oxygen pipelines require oil-free designs to prevent combustion.
- Electropolished or passivated valve bodies and stems, conforming to BS EN ISO 12500 standards, are essential.
- Anti-static designs with conductive springs prevent static buildup.
- Liquefied Natural Gas (LNG) and Cryogenic Gases:
- LNG operations at -162℃ necessitate valves with cryogenic material (ASTM A352 LCB/LC3) and PTFE seals.
- Double or triple offset structures compensate for thermal contraction.
- Waste Gas Treatment (VOCs and Toxic Gases):
- Dual seal structures (metal and fluororubber) achieve near-zero leakage (ISO 15848-1 AH).
- Fire-safe designs with graphite/metal wound seats maintain sealing integrity during fires (API 607).
Core Advantages:
- Corrosion and High-Pressure Resistance:
- Materials like Hastelloy C276, Incoloy 825, and fluoropolymer/ceramic linings handle aggressive media.
- Reinforced valve bodies withstand high pressures (ANSI Class 600).
- High Sealing and Safety:
- Double or triple offset seals minimize wear, extending service life.
- Explosion-proof actuators (ATEX/IECEx) ensure safety in hazardous areas.
- Intelligent Control and Rapid Response:
- Electric actuators enable precise flow control (±1% accuracy).
- Pneumatic valves with quick open/close functions meet SIL 2 safety levels.
Selection Recommendations:
- Media Matching:
- Hastelloy or duplex stainless steel for sulfur-containing gases.
- Oil-free 316L for oxygen.
- LCB/LC3 and PTFE/graphite for cryogenic gases.
- Operating Parameters:
- Multi-layer metal seals for high pressure (PN40+).
- Nickel-based alloys and graphite seals for high temperature (300℃+).
- Safety Compliance:
- ATEX/IECEx actuators for explosive environments.
- API 607 fire-safe certification.
Conclusion:
High-performance butterfly valves are essential in gas chemical plants, offering robust solutions for challenging conditions. Proper selection, considering media composition, operating parameters, and safety standards, enhances plant safety, efficiency, and environmental compliance.