| 摘要 |
PROBLEM TO BE SOLVED: To produce gypsum with high purity and efficiently decrease solid matter of molten fly ash by neither increasing the steps or chemical agents nor clogging a filter. SOLUTION: The method is for recovering gypsum from molten fly ash containing a calcium component, a chlorine component, and a valuable metal component. At first, the molten fly ash is subjected to elution treatment with an aqueous hydrochloric acid-containing solution adjusted at pH7-10 to elute a large portion of the calcium component and the chlorine component from the molten fly ash and obtain an eluting solution. Next, a solid matter containing the remaining of the calcium component and the valuable metal component in the molten fly ash are removed from the eluting solution produced in the elution step 13. Next, sulfuric acid is added to the eluting solution from which the solid matter is removed to cause reaction, precipitate gypsum, and at the same time convert the eluting solution into an aqueous hydrochloric acid-containing solution, a gypsum filtrate. Further, after the precipitated gypsum is separated from the aqueous hydrochloric acid-containing solution, a portion or all of the aqueous hydrochloric acid-containing solution is turned back to the elution step 13. COPYRIGHT: (C)2009,JPO&INPIT
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