NACE MR103 SS Pressure Vessels For Amine Reflux Anti Corrosive U Stamp Approval
Pressure Vessels for Amine Reflux Vessels: Design & Considerations
Amine reflux vessels are pressure vessels designed to handle condensed liquids (water + amine) and residual acid gases (H₂S, CO₂) from the overhead of an amine stripper column. Their design follows strict standards due to corrosive conditions and operational demands.
1. Design Codes & Standards
I.> ASME BPVC (Boiler & Pressure Vessel Code), Section VIII, Div. 1 or 2 – Mandatory for pressure containment.
II.> API 12GDU (Gas Dehydration Units) – Guidelines for amine system components.
III.> NACE MR0175/ISO 15156 – Material selection for H₂S service (sour environments).
IV.> GPSA Engineering Data Book – Industry best practices for gas processing.
2. Key Design Parameters
| Parameter | Typical Range | Notes |
| Design Pressure | 50–150 psig (3.5–10 barg) | Must exceed stripper overhead pressure. |
| Design Temperature | 200–250°F (93–121°C) | Matches stripper condenser outlet. |
| Material | Carbon steel (SS for high corrosion) | Lined or coated if severe H₂S/CO₂. |
| Corrosion Allowance | 1/8" to 1/4" (3–6 mm) | Extra thickness for amine service. |
| Vent Size | 2–6 inches (DN50–DN150) | For non-condensable gas release. |
3. Material Selection
I.> Carbon Steel (SA-516 Gr. 70) – Most common, cost-effective, but requires amine-compatible coatings/inhibitors.
II.> Stainless Steel (SS 304/316) – Used for high H₂S/CO₂ or oxygen-contaminated systems.
III.> Clad Materials (CS + SS overlay) – For severe corrosion zones.
IV.> Internal Linings (Fiberglass, PTFE, Epoxy) – Additional protection against wet acid gas attack.
Note: Amine degradation products (e.g., heat-stable salts) can accelerate corrosion—material choice depends on amine type (MDEA, DEA, MEA).
4. Nozzle & Internals Requirements
| Nozzle | Purpose | Typical Size |
| Inlet | From condenser | 6–12 inches (DN150–DN300) |
| Liquid Outlet | Reflux to stripper | 3–6 inches (DN80–150) |
| Vent | Non-condensable purge | 2–4 inches (DN50–100) |
| Drain | Sludge removal | 2 inches (DN50) |
5. Pressure Relief & Safety
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PSV (Pressure Safety Valve) – Sized per API 520/521 for overpressure scenarios.
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Rupture Disk (Optional) – For additional protection against sudden pressure spikes.
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Flare/Scrubber Vent – Disposes H₂S/CO₂ safely.
6. Operational Challenges & Mitigation
| Issue | Cause | Solution |
| Corrosion | Wet H₂S, heat-stable salts | Use corrosion-resistant materials, monitor amine quality. |
| Foaming | Contaminated amine | Install mist eliminator, add antifoam agents. |
| Level Control Failure | Faulty instrumentation | Redundant level switches (LT, LAL, LAH). |
| Plugging | Degradation products | Regular flushing, filtration. |
7. Inspection & Maintenance
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NDT (UT, RT, PT) – Checks for wall thinning/cracks.
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Thickness Monitoring – Ultrasonic testing (UT) for corrosion tracking.
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Biannual Shutdown Checks – Demister integrity, nozzle condition.
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