Particle impact compatibility assessment of oxygen preheater 304 stainless steel tubes in gaseous oxygen

• Oxygen system operating condition above CGA recommended PV curve. • Particle impact test for material compatibility assessment in gaseous oxygen • Curved radii SS304 tubes – higher frictional path vs. higher impingement angle. • Particle impact testing under transient and steady-state operating conditions. • Higher frictional path showed more particle ignition than higher impingement angle. Oxygen preheaters constructed from stainless steel (SS) 304 tubing with multiple bend radius are known to be operated at temperatures > 250 °C, pressures ∼ 50 bar, and gas velocities of 5–10 m/s across process industries. To improve overall efficiency, there is growing interest in raising these operating conditions to 300 °C and 70 bar, which when compared with Compressed Gas Association’s recommended Pressure-Velocity design curve, exceed suggested velocity limits for minimizing particle impacts. This necessitates rigorous materials compatibility assessment to mitigate ignition and burnout risks. This work examines particle impact (PI) behavior of SS304 tubes using a custom-built test rig, to evaluate how tube geometry (larger- vs. smaller-radii bends) and operational mode (transient vs. steady flow) affect likelihood of particle ignition and tube kindling. Under transient flow, tubes with larger-radius bends (larger fractional path) exhibited more pronounced iron-particle ignition than those with smaller-radius bends (higher impingement angle), producing molten slag resulting in localized heat-affected zone (∼100 µm) on tube wall. In contrast, no particle ignition occurred under steady flow or when using inert particles. Overall, insights from this study provide a foundation for effective PI testing of curved tubes and supports more informed design and safer operation of oxygen preheaters, when extending beyond conventional guidelines.