Desalination Brine Concentrators: 2507 vs. Alloy 625 Performance

 

Why super duplex 2507 dominates evaporator tubes?
PREN 42 withstands 300,000 ppm chlorides at 80°C. Yield strength 550 MPa handles thermal stresses. Costs $25/kg vs. Alloy 625's $120/kg. Proven 10-year service in MED plants.

 

When Alloy 625 is required for scaling control?
For silica-rich brines (>500 ppm SiO₂) where under-deposit corrosion occurs. Nickel-chromium matrix resists acidic scale removers (pH 1.5) better than stainless.

 

Maximum flow velocity limits?
Minimum 1.2 m/s prevents particulate settlement. Maximum 2.8 m/s for 2507, 4.5 m/s for Alloy 625 before erosion-corrosion accelerates.

 

Scaling mitigation strategies?
Antiscalant dosing (PPCA or HEDP). Pulsed flow cleaning every 8 hours. Electropolished surfaces reduce adhesion 70%. Online chlorination controls MIC.

 

Failure analysis protocol?
UT wall thickness mapping at bends. Scale composition analysis (Ca/Si/Cl). SEM-EDS of pitted areas. Corrosion potential logging during CIP cycles.