China Nonferrous Metallurgy

The high-temperature melting and harmless disposal of incineration fly ash can achieve the decomposition of organic compounds such as dioxins and the solidification of heavy metal elements. The degree of harmless disposal of fly ash is high, but the large amount of chloride salts contained in fly ash will greatly hinder the melting process. This article aims to separate slag and salt melting in fly ash, and designs and selects an ideal low melting point slag type, CaO-FeO-SiO2-Al2O3-Fe2O3 five element slag, CaO∶SiO2∶FeO∶Al2O3∶Fe2O3=36∶34∶21∶7∶2, the complete melting temperature of the slag is around 1250℃. The results of the hot state test indicate that the optimal slag ratio scheme effectively suppresses the volatilization of chloride salts while achieving efficient separation of slag and salt. After the melting and separation of slag salt, the proportion of Cl, Na, and K elements enriched in the molten salt phase reaches 76.40%, 97.54%, and 88.19%, respectively. Slag water quenching achieves solidification of heavy metals such as Pb and Zn. Compared with raw material fly ash, the leaching concentration of Pb, Zn, Cr and other elements in water quenched slag can be reduced by 99.48%, 90.00%, and 72.00%, respectively. The leaching toxicity test of water quenched slag meets the requirements of vitrified products. After separating fly ash salt, the tailings and incineration bottom slag can be co processed to prepare vitrified products, which can achieve “zero emission” of ash in the process of garbage incineration power generation.