Effect of flotation on the dioxin distribution in size-fractioned fly ash of hospital solid waste incineration

ABSTRACT

After the flotation of hospital solid waste incinerator (HSWI) fly ash, two types of solid products, froths and tailings, are produced. This paper reports the effect of flotation on the dioxins distribution patterns in different particle size fractions (−25, −38, +25, −75, +38, −106, +75 and +106 µm) of fly ash. The results showed that the froths had a higher small-size particle distribution than that of the raw fly ash. The dioxin content with particle size in the flotation products depended on the partition behavior of powder-activated carbon (PAC). The dioxin content in the fine particles of the froths was higher than that in the coarse particles, and the highest content was in the finest particles (−25 µm). The dominant dibenzo-p-dioxins and dibenzofurans (PCDD/F) congeners in the froths and tailings were similar to those in the raw fly ash. A positive correlation between carbon removal and PCDD/F removal with different size fractions was observed. The carbon removal efficiencies of the fractions of −25 and −38, +25 µm were evidently higher than those of the other particle size fractions. Similarly, the PCDD/F removal efficiencies in fractions of −25 and −38, +25 µm could reach 156.9% and 115.0%, respectively.

KEYWORDS:

• Carbon constituents
• fly ash
• flotation
• PCDD/Fs
• size distribution

Acknowledgements

The authors gratefully acknowledge the National Natural Science Foundation of China under grant under the project number NSFC 51378332, National key research and development program number 2017YFC0703100, Tianjin science and technology correspondent project number 16JCTPJC50300.