Effect of Composite Fluxing Agent on Melting Temperature and Phase of Fly Ash from Waste Incineration.

High temperature melting vitrification is the safest and harmless disposal technology for fly ash from hazardous waste incineration. Fly ash with high calcium content was used as the research object to melt fly ash with low temperature by introducing SiO₂, H₃BO₃ and CaF₂ fluxing agents. The melting temperature, phase change and heavy metal leaching of fly ash were characterized by X-ray diffractometer, ash melting point analyzer and inductively coupled plasma atomic emission spectrometer. The results show that when the alkalinity of fly ash is adjusted to 1.10 by SiO₂ (27.9%, mass fraction), CaSiO₃ minerals with low melting point are formed, and the melting point of fly ash decreases from above 1 400 °C to 1 300 °C. H₃BO₃ (4.5%, mass fraction) and CaF₂ (7.0%, mass fraction) are introduced as fluxing agents, and the melting temperature is further reduced to 1 200 °C, but SiO₂ is overdoped. After optimization, the composite fluxing agent formula is SiO₂ (20.0%, mass fraction), H₃BO₃ (4.5%, mass fraction) and CaF₂ (7.0%, mass fraction), and the minimum melting temperature of fly ash is 1 124 °C, the vitreous content of the melt product reaches 87% (mass fraction), and the harmful substances of acid leaching are lower than the limit value, meeting the technical requirements of GB/T 41015-2021 standard for vitrification products. [ABSTRACT FROM AUTHOR]