Pipe fittings for wet FGD SO₂ scrubbers — absorber spray headers, recirculation lines, gypsum slurry handling, and mist eliminator wash systems. Hastelloy C-276 for the most aggressive chloride zones. 254 SMO and Super Duplex 2507 for lower-chloride FGD service. 316L is not suitable for wet FGD environments.
Request FGD Fittings QuoteWet FGD scrubbers process flue gas from coal, oil, or waste combustion. The scrubber liquor is a cocktail of corrosives:
SO₂, SO₃ dissolved in water → H₂SO₄ / H₂SO₃. pH typically 4–6 in absorber zone.
Coal chloride concentrates in scrubber liquor — chloride levels 10,000–100,000 ppm common. Pits 316L rapidly.
CaSO₄·2H₂O gypsum in recirculation — erosion-corrosion at elbows and tees.
| FGD Zone / Service | Typical Cl⁻ (ppm) | Recommended Material | EN W.Nr. | Notes |
|---|---|---|---|---|
| Absorber spray headers | 50,000–150,000+ | Hastelloy C-276 | 2.4819 | Highest corrosion risk zone — C-276 standard |
| Recirculation pump casing trim | 50,000–150,000+ | Hastelloy C-276 | 2.4819 | Pump trim: C-276 or C-22 alloy |
| Mist eliminator headers | 10,000–80,000 | Hastelloy C-276 or 254 SMO | 2.4819 / 1.4547 | C-276 for high Cl⁻; 254 SMO for moderate |
| Gypsum slurry lines | Moderate | 254 SMO or Super Duplex 2507 | 1.4547 / 1.4410 | PRE ≥40 minimum; rubber-lined CS also used |
| Clean liquor return | 10,000–30,000 | Super Duplex 2507 or 254 SMO | 1.4410 / 1.4547 | Lower severity — PRE ≥40 sufficient |
| Oxidation air spargers | Moderate | 254 SMO | 1.4547 | Submerged in absorber — PRE ≥43 specified |
| Stack gas outlets (dry) | Low | 316L or CS (coated) | 1.4404 | Dry post-scrubber gas — less aggressive |
| Limestone feed slurry | Low | 316L or rubber-lined CS | 1.4404 | Mildly abrasive — SCC not a concern |
The industry standard for FGD absorber spray headers and recirculation pump trim. Resists HCl, H₂SO₃, H₂SO₄, and very high chloride scrubber liquor. No other alloy provides this breadth of resistance at comparable cost.
6% Mo super-austenitic. PRE ≥43 — suitable for moderate-chloride FGD zones (gypsum slurry, clean liquor, mist eliminators). Step up from Super Duplex with better high-temperature pitting resistance.
PRE ≥40. Used for gypsum slurry lines and lower-chloride FGD circuits where 254 SMO is specified. Higher strength allows thinner walls in large-bore gypsum recirculation headers.
Higher Cr than C-276 — better resistance to mixed oxidising/reducing environments. Preferred over C-276 where HNO₃ is co-present (waste-to-energy FGD). Used as C-276 alternative in EU refinery FGD.
25Ni-20Cr-4.5Mo-Cu. PRE ~33. Marginal for high-chloride FGD absorber zones — used in earlier FGD designs. C-276 and 254 SMO have superseded 904L in most modern FGD applications.
316L pits rapidly in FGD absorber liquor — chloride concentration and SO₂ combination overcomes its corrosion resistance. Only acceptable for dry FGD zones (stack outlet, dry limestone feed) with low chloride.
FGD absorber spray headers are the most corrosion-critical zone in a wet limestone scrubber — the spray liquor contains dissolved SO₂, H₂SO₃, and concentrated chlorides from the coal. The industry standard is Hastelloy C-276 (EN 2.4819, UNS N10276). It provides reliable resistance to the combined HCl + H₂SO₃ environment at 40–60°C, including resistance to pitting, crevice corrosion, and SCC. Hastelloy C-22 (2.4602) is used as an alternative in waste-to-energy FGD where oxidising conditions (HNO₃) are also present. 254 SMO (PRE ≥43) is sometimes used for lower-chloride spray zones, but C-276 is preferred where chloride data is uncertain.
316L (EN 1.4404, PRE ~24) is NOT suitable for wet FGD absorbers because the scrubber liquor combines SO₂, SO₃, SO₄²⁻, HCl (from coal chloride concentrated in the liquor — often 10,000–100,000 ppm), HF, and gypsum slurry. This multi-acid high-chloride environment is far above 316L's corrosion threshold. Pitting, crevice corrosion, and SCC occur within months in 316L absorber components. The minimum practical material for wet FGD spray headers is 254 SMO (PRE ≥43) or Super Duplex 2507 (PRE ≥40), with Hastelloy C-276 required in the highest-chloride zones.
Yes. All nickel alloy (Hastelloy C-276, C-22) and high-alloy stainless (254 SMO, Super Duplex 2507) fittings are supplied with EN 10204 3.1 as standard. EN 10204 3.2 with TPI witness (TUV, Lloyd's Register Asia, BV) is available on request for PED Category III–IV applications. For EU power plant FGD covered under PED, specify your PED category, design pressure, and temperature in the RFQ so we can confirm the appropriate certificate level. Include the specific FGD zone (absorber spray, recirculation, gypsum slurry, etc.) to allow material grade confirmation.
