Characteristics of arsenic migration in MSWI fly ash during co-processing with a cement kiln

The migration characteristics of arsenic during the co-processing of municipal solid waste incinerator (MSWI) fly ash in a cement kiln were investigated. Emission data of arsenic from the cement kilns which co-processed waste materials were analyzed statistically to investigate the effect of total arsenic input and total chloride input. An equilibrium analysis of arsenic was performed using the thermodynamic equilibrium software CHEMKIN. A simplified model of cement kiln was used to investigate the effect of kiln dust circulation on the migration characteristics of arsenic. The results show the exchangeable, water and acid-soluble phase, the easily reduced phase and the oxidizable phase of arsenic in MSWI fly ash were 28.55%, 20.72% and 65.33% respectively according to the BCR sequential extraction procedure. CaO has a dramatic effect on the thermodynamic behavior of arsenic, while chloride has little effect. Because the main component of the cement raw meal is CaCO₃, which generates a large amount of CaO after decomposition, it reacts with arsenic to form stable Ca₃(AsO₄)₂. The "single stabilization rate" of arsenic was approximately 65% during the sintering process. The model calculation show the As concentration increased in both kiln dust and clinker after the substitution of cement raw meal with MSWI fly ash at 1%. Kiln dust circulation increased the stabilization of As in clinker.