Stainless Steel, Duplex and Nickel Alloy Pipes for Flue Gas Desulfurization and Environmental Protection
Recommended Pipe & Tube Materials
Environmental systems, especially wet flue gas desulfurization (FGD) scrubbers, create highly corrosive conditions: acidic condensate, high chloride concentrations, abrasive limestone slurry and temperature swings. This article explains how duplex stainless steel and nickel alloy pipes are selected for FGD and other environmental protection applications.
Why FGD Is So Corrosive
- Low pH from absorbed SO₂ and acid condensate
- High and rising chloride levels as scrubber liquor is recirculated
- Abrasive slurry of limestone and gypsum that causes erosion-corrosion
- Wet/dry transitions and hot spots where corrosive deposits concentrate
- Fluctuating operation with upsets, start-ups and shutdowns
Materials by Area
| Area | Typical materials |
|---|---|
| Slurry recirculation and spray headers | Duplex 2205, super duplex 2507, or rubber-lined / FRP alternatives |
| Absorber internals, mist eliminator supports | Duplex, 6Mo, Alloy 625, C276 |
| Wet-dry interface, inlet duct, outlet ducts | Alloy C276, C22, Alloy 59 or clad/lined constructions |
| Wastewater treatment (FGD blowdown) | 6Mo, super duplex, C276 depending on chloride level |
| General water and process lines | 316L, 317L, 2205 |
Duplex 2205 and 2507 offer a strong balance of erosion resistance, strength and chloride resistance for slurry and liquor lines. When chloride and acidity rise, or in wet/dry interface zones, 6Mo and nickel-chromium-molybdenum alloys such as C276, C22 and Alloy 59 are preferred.
Beyond FGD: Other Environmental Applications
- Waste-to-energy plants: boiler tubes and flue gas cleaning lines subject to chlorides and acid gases
- Wastewater and sludge treatment: duplex and 316L pipes for aggressive or high-chloride effluent
- Chemical scrubbers and gas treatment: nickel alloys for acidic, oxidizing conditions
- Biogas and landfill gas systems: stainless steel for wet, corrosive gas lines
Relevant Standards
- ASTM A790 / A928 (duplex pipe), ASTM A312 (austenitic pipe)
- ASTM B622 / B619 (Alloy C276, C22) and ASTM B444 (Alloy 625)
- Project and plant specifications for pressure and design, such as ASME B31.3
Selection Tips
- Get the scrubber chemistry: chloride concentration, pH, temperature and solids content
- Consider both normal and upset conditions, including start-up and shutdown when acidic condensate forms
- Compare total lifecycle cost of solid alloy, clad or lined pipe with alternatives such as rubber-lined or FRP
- Use appropriate welding and post-weld cleaning to prevent localized attack at weld zones
- Email: info@duplex-stainless-steel.com
- WhatsApp / WeChat: +86-13587686960
- Send Your Inquiry →
Frequently Asked Questions
Q1: What is the best pipe material for FGD slurry lines?
Duplex 2205 or 2507 is commonly used because of good erosion resistance and chloride tolerance. In the most acidic or high-chloride zones, nickel alloys like C276 or Alloy 59 provide additional margin.
Q2: Why use Hastelloy C276 in FGD systems?
C276 has outstanding resistance to acidic, chloride-rich and oxidizing conditions, including the wet/dry zones where other alloys can suffer severe localized corrosion.
Q3: Is stainless steel pipe better than FRP or rubber-lined pipe for FGD?
It depends on temperature, pressure, erosion and cost. Alloy pipes offer strength, heat resistance and long service life, whereas lined or FRP pipes may be cheaper initially in some services. A lifecycle cost comparison is recommended.
Q4: Can you supply large-diameter pipe for FGD projects?
Please specify the diameter range, wall thickness and quantity, and we will confirm the best manufacturing route.
Request a Quote for FGD and Environmental Pipes
Send us your application area, grade, standard, OD × wall thickness × length and quantity, and we will reply with a recommendation and pricing within 24 hours.