| 摘要 |
PROBLEM TO BE SOLVED: To make dioxins contained in fly ash harmless by decomposition by heating them at a specific temperature or higher by adding an oxidative acid. SOLUTION: Making dioxins harmless is carried out by adding an oxidative acid to fly ash containing dioxins and treating them as a slurry by heating. Examples of preferable oxidative acids are sulfuric acid, nitric acid, or mixed acid of sulfuric acid and nitric acid, etc. Concentration of the acid is suitably 80wt.% or higher sulfuric acid and 50wt.% or higher nitric acid, and 95wt.% or higher concentrated sulfuric acid and 60wt.% or higher concentrated nitric acid are preferable. Further, in the case where sulfuric acid of near 80wt.% concentration or nitric acid of near 50wt.% concentration is used, that is preferably treated by heating while water is vaporized. Dioxins can be decomposed since the acid is concentrated by evaporation of water. The heating temperature is suitably 100 deg.C or higher since a water content in the added acid is preferably vaporized. The heating temperature is suitably 100 deg.C or higher up to and including 120.5 deg.C for nitric acid, and further preferably 250 deg.C or higher for sulfuric acid. |
