| dc.description.abstract | Incineration of waste generates highly toxic fly ash. Given Taiwan′s limited land and dense population, traditional cement solidification and landfill methods can no longer accommodate the increasing fly ash production. Finding effective treatment and disposal methods has become an unavoidable challenge, and achieving the goal of fly ash reuse has emerged as a new trend. In recent years, development of innovative air pollution control technologies coupled with the replacement of alkaline sorbents, have significantly altered the composition of incineration fly ash. This study aims to apply low-temperature pyrolysis as a method for treating incineration fly ash, reducing the concentration of PCDD/Fs in the fly ash to meet the EU-EoW criteria (≤ 20 pg TEQ/g). The study calculates the chlorination degree of PCDD/Fs in the samples while examining the differences in the physicochemical properties and degradation mechanisms of the two types of fly ash. The results show that all samples experienced a reduction in chlorination degree after pyrolysis, with the concentration of species trending towards lower-chlorinated compounds, indicating that dechlorination was the primary reaction mechanism. Sodium-based fly ash achieved over 99% removal efficiency of PCDD/Fs based on mass concentration when operated at 350°C. The toxic equivalency concentration decreased to 0.0059, 0.0013, and 0.0011 ng I-TEQ/g after reaction of 5, 15, and 30 minutes, respectively, meeting the EU-EoW criteria. Subsequent combination with water washing techniques further improved PCDD/Fs removal efficiency, especially for calcium-based fly ash at 300°C, confirming the influence of chloride content on removal efficiency. In summary, sodium-based fly ash generally exhibited better dioxin removal efficiency compared to calcium-based fly ash. This is likely due to the differences in chloride content and the composition of metal compounds in the fly ash. Additionally, the distribution of gaseous and solid-phase dioxins in pyrolysis revealed that 0.19% of the mass concentration was desorbed, accounting for 1.91% of the toxic equivalency concentration, translating to an exhaust emission concentration of 0.44 ng I-TEQ/Nm3. This study provides insights into domestic waste disposal methods, demonstrating that fly ash pyrolysis technology holds significant potential for future waste management in Taiwan. | en_US |