Decomposition of Dioxins in Fly Ash with Supercritical Water Oxidation.

Abstract

In this study, we tried to decompose the dioxins in a fly ash using supercritical water and an oxidizer. The first objective is to compare the decomposition efficiency of the dioxins in the fly ash with that in the pulp mill sludge, because the distribution pattern of the dioxin isomers in the fly ash (called incineration pattern) is quite different from that in the pulp mill sludge (pulp bleaching pattern) (Hiraoka, 1993), that is, the former has many kinds of dioxin isomers and the latter contains relatively high concentrations of tetrachlorodibenzofuran and tetrachlorodibenso-p-dioxin. The second objective is to check the possibility of the decomposition of dioxins at around 673 K because a conventional stainless steel can be used as a construction material for the decomposition reactor in a very dilute aqueous region of hydrogen chloride. The third objective is to examine what kind of oxidizer is suitable for rapid and complete decomposition of the dioxins.