Valves for Acetic Acid (CH₃COOH) Service
Acetic acid is a key industrial chemical used as a solvent and as feedstock for PTA (purified terephthalic acid), vinyl acetate monomer, cellulose acetate, and acetic anhydride. Glacial (anhydrous) acetic acid is the most corrosive form; dilute acetic acid (food-grade vinegar) is mild. In PTA oxidation reactors, acetic acid is combined with para-xylene and air at 180–200°C and 15–20 barg — one of the more demanding valve environments, requiring titanium or Hastelloy C-276 for the most aggressive circuits.
Pressure Range
1–25 barg (storage, transfer, PTA oxidation reactor)
Temperature
Ambient to +220°C (PTA oxidation circuit)
Industries
PTA / polyester production, Vinyl acetate monomer, Acetic anhydride
Key Properties — Acetic Acid (CH₃COOH)
- Corrosivity increases with concentration and temperature
- Flash point: 40°C (glacial) — flammable, ATEX Zone 1 in production areas
- Attacks most metals in hot, concentrated form
- PTA oxidation: acetic acid + p-xylene + air at 180°C, 15–20 barg — extremely corrosive
- Food-grade dilute acetic acid (vinegar) is benign at ambient temperature
Material Compatibility — Acetic Acid (CH₃COOH)
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 |
|---|---|---|
| Hastelloy C-276 | Excellent | Best choice for glacial and hot acetic acid in PTA oxidation service. |
| Titanium Gr 2 | Excellent | Excellent for hot acetic acid, especially in PTA oxidation reactors. |
| SS 316L | Fair | Acceptable for dilute (<30%) cold acetic acid. Not for hot concentrated service. |
| Carbon Steel | Poor | Severely attacked by all concentrations of acetic acid. |
| PTFE-lined | Excellent | Excellent for all concentrations at moderate temperature. |
Recommended Valves
Ball Valve (Hastelloy C-276 or Ti body)
Isolation in PTA oxidation and hot acetic acid circuits
Gate Valve (Hastelloy or SS 316L)
Mainline isolation for acetic acid storage and transfer
Globe Valve (Hastelloy, Stellite trim)
Control service in PTA plant acetic acid recycle circuits
PTFE-lined Butterfly Valve
Large-bore acetic acid service where Hastelloy is cost-prohibitive
Diaphragm Valve (PTFE diaphragm)
Accurate control of acetic acid dosing and blending
Valves to Avoid
Carbon steel valves — severely corroded
Bronze/brass — attacked by acetic acid
SS 316 for hot concentrated service without corrosion allowance review
Special Considerations
Applicable Standards
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