Application of non-thermal plasmas on toxic removal of dioxin-contained fly ash

Abstract

In this paper, non-thermal nanosecond plasma has been applied to detoxicate dioxin-contained fly ash. The experimental results show that a positive pulse discharge provides a higher destruction effect on the compounds contained than does a negative one. Products after discharge are discussed and analyzed in detail. It was found that different isomer compounds show different toxic removal effects, and the higher the toxicity of the compounds is, the higher is the destruction efficiency. The destruction efficiency ranges from 80% to 20%. For dioxin congeners, the efficiency from high to low can be arranged as an order of T 4CDDs, P 5CDDs, H 6CDDs, H 7CDDs and O 8CDD and for the furan ones as T 4CDFs, P 5CDFs, H 6CDFs, H 7CDFs and O 8CDF. Among all of the isomers contained in the fly ash, the 2, 3, 7, 8-T 4CDD compound which has the highest toxicity shows the highest destruction efficiency up to 81%. It was also found that ordinarily, with the increase of the concentration of the toxic compounds, the destruction efficiency increases. Based on the content analysis of the ambient air after discharge in an airproof container, the destruction effect on dioxin compounds in the fly ash has been further confirmed. From these results, we are looking forward to finding out methods of higher toxic removal, and the application of non-thermal plasma technology on detoxification of dioxin-contained flue gas or fly ash before they are released into the atmosphere or are buried into the ground is highly expected.