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.