Effect of Different Oxide Additives on Migration Behavior of Heavy Metals of MSWI Fly Ash in Swirling Melting Furnace

The effects of different oxide(CaO, SiO2 and MgO) on heavy metals migration behavior of municipal solid waste incinerator(MSWI) fly ash were investigated in a self-designed 0.2MW swirling furnace during melting process. The results show that the emission of heavy metals could be inhibited when CaO doping amount is 5%. Doping SiO2 and MgO in fly ash is advantageous to migration heavy metals in slag. With the doping amount of SiO2 increasing, the percentages of As, Cd, Zn and Pb were reduced in the flue gas. And the rate of Cu, Co, Mn in the slag is significantly increasing. The percentage of heavy metals content in the flue gas is decreased at first and then increased with the increase in MgO doping, at about 10% to a minimum. When the doping amount of MgO is 10%, most of As, Zn, Cd, Pb and Hg are migrated to the molten fly ash or flue gas, descending order, HgAsZnPbCd. The percentage migration of Cu, Co and Mn in the slag is the range of approximately 45.5%-59.4%, while the proportion in the flue gas is 23.8%-26.3%. XRD analysis show that with the fly ash doping 5% CaO, the slag contains CaSiO3, CaAl2Si2O8, Ca2Al2SiO7, and Fe2SiO4. With the increase in doping SiO2, slag Ca2Al2SiO7, CaSiO3 declining share of such crystals. It is conductive to the formation of slag glassy amorphous substance. Increase in the proportion of SiO2adding fly ash could significantly improve the proportion of heavy metals transfer to the slag. When the MgO content in the samples dope is 10%, the main crystalline phases in slagare(MgFe)2SiO4, Fe3Al2Si3O12, and Ca2MgSi2O7, the slag is in preferably vitrification.