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Arsenic Partitioning Behavior During Sludge Co-combustion: Thermodynamic Equilibrium Simulation

Liu, Jingyong, Xie, Candie, Xie, Wuming, Zhang, Xiaochun, Chang, KenLin, Sun, Jian, Kuo, Jiahong, Xie, Wenhao, Liu, Chao, Sun, Shuiyu, Buyukada, Musa, Evrendilek, Fatih
Waste and biomass valorization 2019 v.10 no.8 pp. 2297-2307
air, aluminum oxide, arsenic, arsenic oxide, calcium oxide, carbon dioxide, chlorides, combustion, ferric oxide, nitrogen, oxygen, sewage sludge, silica, thermodynamics, volatilization
Using the computation method of thermodynamic equilibrium, effects of sewage sludge (SS) co-combustion conditions and interactions with Fe₂O₃, SiO₂, CaO and Al₂O₃ on migration and transformation of arsenic (As) were simulated in oxy-fuel (CO₂/O₂) and air (N₂/O₂) atmospheres. Arsenic mainly existed as As(s), As₄(g), As₂O₅(s), As₄O₆(g) and AsO(g) and volatilized more easily in reducing than oxidizing atmosphere. Increased O₂ concentration slowed down the formation rate of AsO(g), thus reducing the volatilization rate of As. With the increased pressure, the conversion rate of As₂O₅(s) into As₄O₆(g) accelerated. In the multi-chemical system of SiO₂, Al₂O₃ and CaO, As reacted with CaO and Al₂O₃ to form AlAsO₄(s) and Ca₃(AsO₄)₂(s) which inhibited As volatilization. SiO₂ prevented As from reacting with CaO to generate Ca₃(AsO₄)₂(s). Fe₂O₃ affected reactions between Al₂O₃(CaO) and As which inhibited As volatilization. In the whole SS co-combustion system, As reacted with O₂ but had a weak affinity with Cl and with no arsenic chlorides observed.