Q1: What materials handle supercritical CO2 at 700°C/250 bar?
A1: Nickel-based superalloys (Inconel 617, Haynes 230) are required for these extreme conditions. They maintain strength while resisting carburization. Advanced austenitic steels (HR6W) are being developed as lower-cost alternatives. Material selection balances cost against expected system lifespan.
Q2: How does CO2 purity impact material selection?
A2: Even ppm-level contaminants (H2O, O2) dramatically increase corrosion rates. Higher alloys are needed when purification isn't perfect. Online monitoring ensures purity remains within design limits. This interplay between materials and chemistry is critical for economic operation.
Q3: What are the unique design challenges for sCO2 piping?
A3: High fluid density requires robust support designs. Rapid property changes near the critical point demand careful modeling. Leak prevention is paramount given the high pressures. These factors make sCO2 systems more complex than traditional steam plants.
Q4: How are thermal stresses managed in sCO2 systems?
A4: Optimized routing minimizes constraint points. Flexible couplings accommodate thermal movement. Advanced FEA analysis predicts stress concentrations. These approaches prevent fatigue failures during temperature cycling.
Q5: What inspection methods monitor sCO2 pipe condition?
A5: Ultrasonic testing tracks wall thickness changes. Replication metallurgy examines microstructural evolution. Specialized NDT detects creep damage. These methods help predict remaining service life.
