Valves for Amine (DEA / MEA / MDEA — Gas Sweetening) Service
Amine solutions — diethanolamine (DEA), monoethanolamine (MEA), and methyldiethanolamine (MDEA) — are used extensively in natural gas and refinery gas sweetening units to remove hydrogen sulphide (H₂S) and carbon dioxide (CO₂) from sour gas streams. The amine absorber and regenerator are among the most demanding corrosion environments in a gas plant.
Pressure Range
Absorber: 30–100 bar; Regenerator: 1–2 bar (vacuum flash)
Temperature
Absorber: 35–65°C; Regenerator reboiler: up to 135°C
Industries
Natural gas sweetening (H₂S and CO₂ removal), Refinery FCC off-gas treating, Hydrogen plant feed gas treating
Key Properties — Amine (DEA / MEA / MDEA — Gas Sweetening)
- Amine concentration: typically 30–50 wt% in water
- Absorber conditions: low temperature (35–60°C), high pressure (up to 100 bar)
- Regenerator: high temperature (110–130°C), low pressure (1–2 bar), highly corrosive
- Rich amine (carrying H₂S + CO₂) is significantly more corrosive than lean amine
- Heat stable salts (HSS) accumulate in amine — accelerate corrosion if not removed
- SSCC (Sulphide Stress Corrosion Cracking) risk in sour service components
Material Compatibility — Amine (DEA / MEA / MDEA — Gas Sweetening)
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| Carbon Steel (WCB/A105) | Good | Acceptable for lean amine at low temperature with velocity limits <3 m/s. Not for rich amine regenerator. |
| SS 316L | Excellent | Standard material for rich amine, regenerator, and reboiler service. |
| SS 304L | Good | Acceptable for lean amine; 316L preferred in hot rich amine. |
| Duplex SS 2205 | Excellent | Excellent corrosion resistance in amine; sometimes used for critical valves. |
| PTFE seats | Good | Acceptable for lean amine at low temperature; check chemical compatibility at regenerator conditions. |
| Hastelloy C-276 | Excellent | Used for hottest, most corrosive amine service points. |
Recommended Valves
Ball Valve (SS 316L body, PTFE seats, NACE MR0175 trim)
Standard isolation for amine absorption and regeneration circuits in sour service.
Globe Valve (SS 316L, NACE-compliant)
Flow control on amine recirculation, lean/rich heat exchanger bypass.
Gate Valve (SS 316L, OS&Y, NACE)
Large-bore isolation on amine contactors and regenerator columns.
Control Valve (SS trim, NACE MR0175, anti-cavitation)
Rich amine level control on absorber — prone to cavitation due to pressure drop.
Valves to Avoid
Carbon steel valves in rich amine at high temperature (corrosion rates >1 mm/year)
Copper alloy valves (amine attacks copper)
Valves with hardened trim above NACE MR0175 limit (22 HRC maximum for wetted metal parts)
Elastomeric seals not rated for H₂S/amine co-service
Special Considerations
Applicable Standards
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