Glassy Slag Production From Municipal Solid Waste Incineration Fly Ash Vitrified By Plasma

With the spreading of municipal solid waste incineration?MSWI?,the safety treatment of fly ash has become a key issue concerning secondary pollution.Plasma melting technology can effectively stabilize heavy metals,decompose dioxins.At present,some scholars all over the world paid more attention to this field.But few studies focus on the impact of fly ash composition on glassy slag formation,especially with the CaO-Al₂O₃-SiO₂?CAS?ternary phase.The glass slag formation condition based on CAS ternary phase was mainly studied in the paper.The fly ash which was taken from a municipal solid waste incineration plant in Tianjin as the feedstock,the glass frit and Al₂O₃ as additive agent.The effect of melting temperature,melting time and the ratio of CAS ternary phase was studied.The potential ecological and environment risk of heavy metals in glass slag is carried out by the Synthesis Toxicity Index Model?STIM?.The main conclusions are as follows:The ideal condition for glass slag formation based on CAS ternary phase is CaO 21.78 wt.%³9.04 wt.%,Al₂O₃ 8.22 wt.%²8.37wt.%,SiO₂ 37.66 wt.%⁶8.92 wt.%.Melting time and melting temperature has little effect on glassy slag formation.The heavy metal content in glassy slag follows the order:Zn>Ni?Cr>Cu>Pb>Cd,and the solidified rate follows the order:Ni>Cr>Cu>Zn>Pb.The heavy metal of Ni and Cr are difficult to volatilize,the Pb and Cd are easily to volatilize,the Cu and Zn are semi-volatilize.After plasma melting,the heavy metal specification transforms from unstable fraction?acid soluble fraction,reducible fraction and oxidisable fraction?to stable fraction?residual fraction?,reducing the potential ecological and environment risk.The migration rule of main chemical composition in process of glass slag formation is volatile element?Cl and S?>semi-volatile element?Na,Mg and K?>hard volatile element?Al,Si,Ca,P and Fe?.The glassy slag formation based on CAS ternary phase,the potential ecological and environment risk of heavy metals in glass slag and the migration rule of main chemical composition in glass slag formation process were studied,which provide theoretical guidance for the plasma melting fly ash in industry scale.