| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for recovering phosphorus from sludge incineration ash by which calcium phosphate can be recovered from the sludge incineration ash at a high recovery rate. SOLUTION: Mixed slurry is prepared by mixing the sludge incineration ash and a reaction liquid containing a hydroxide of an alkali metal or an alkaline earth metal in such a ratio that sludge incineration ash/reaction liquid is 0.02-0.2 kg/L. Thereby, phosphoric acid components are extracted into the liquid, and then the mixed slurry is solid-liquid separated into an extraction liquid containing the phosphoric acid components and a dephosphorized ash cake. After that, dephosphorized ash having a water content of≤60% is obtained by subjecting the separated dephosphorized ash cake to washing/solid-liquid separation. On the other hand, to the extraction liquid, Ca(OH)<SB>2</SB>is added and allowed to react with the phosphoric acid components, and the resulting extraction liquid is solid-liquid separated into a calcium phosphate cake and a regenerated liquid containing hydroxide ion. Calcium phosphate having a water content of≤60% is obtained by subjecting the calcium phosphate cake to washing/solid-liquid separation. Further, the regenerated liquid is circularly used as the reaction liquid. COPYRIGHT: (C)2008,JPO&INPIT
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