Effect of additives and steam on chlorine transformation during plasma melting of fly ash

In the process of fly ash melting by plasma technology, additives are usually added to improve the melting characteristics of fly ash and reduce the leaching toxicity of heavy metals, thus reduce energy consumption and pollution risk. However, the effect of additives on the migration and transformation of chlorine salts in fly ash during the melting process is rarely reported. In this study, the effect of additives (SiO₂, Al, B₂O₃, bottom slag collected from the same incinerator) on the migration and transformation of chlorine was investigated by experiments and thermodynamic analysis, and the promotion mechanism of water vapor atmosphere on the migration and transformation of chlorine was also discussed. Soluble chloride is transformed into insoluble chloride during plasma melting of fly ash, B₂O₃ and Al play a role in solidification of the chloride in fly ash, SiO₂ promotes the volatilization of heavy metal chloride salts, the co-melting of fly ash and its homologous bottom ash significantly promotes the reduction of soluble chloride in fly ash, and the content of soluble chloride in fly ash is reduced from 22.39% to 2.2% with the addition of 20% bottom ash. Steam can be used as an inducer and vaporizer to further promote the chlorine volatilization.