Temperature-gradient condensation promotes As2O3 particle growth to reduce the escapable risk.

Volatile As2O3 from high-temperature processing can condense into fine arsenic-bearing particles during flue-gas cooling, increasing mobility and escape tendency. Here, A double-tube, dual-temperature-zone system regulated As2O3 growth under natural cooling, temperature-gradient condensation, and SO2 coexistence. Natural cooling produced limited growth, increasing mean particle size from 17.44 to 33.97 μm and forming irregular deposits through dispersed condensation. By contrast, volatilization at 600°C followed by condensation at 200°C increased mean particle size to 267.28 μm, 15.32 times that of the initial particles, and produced regular octahedral crystals. Under 15% SO2, mean particle size decreased to 230.49 μm but remained substantially larger than under natural cooling. Density functional theory calculations showed that SO2 interacted weakly with the As2O3 surface through van der Waals forces, altering surface energy and electronic structure and thereby affecting surface deposition and continuous growth. A size-dependent attenuation model yielded relative physical escapability indices of 0.6373 for natural cooling, 0.0026 for temperature-gradient condensation, and 0.0064 under SO2 coexistence. These results demonstrate that temperature-gradient condensation converts fine As2O3 condensates into larger particles and markedly reduces the model-estimated physical escapability of arsenic-bearing particles, providing a basis for particle morphology regulation and risk-oriented process control in the cooling section of arsenic-bearing flue gas.