| 摘要 |
<p>PURPOSE:In refluxing a supernatant liquid of an extracted solution and/or a filtrate of an insoluble residue to an extraction tank having a small ratio of extracted solution/slag, to extract and to recover an alkali metal efficiently, by specifying the pH of the extracted solution in the tank. CONSTITUTION:A ratio of water in the extraction tank 1, namely, a ratio of circulated solution/slag is made small to about 1.5-4, and a supernatant liquid of an extracted solution in the thickener 4 and/or a filtrate of an insoluble residue separation of the separator 5 are partially refluxed to the tank 1. An apparent ratio of a refluxed solution + the circulated solution to slag is made >=4, so that the extracted solution is stirred smoothly. A CO2-containing gas is fed to the tank 1 by the vapor-liquid contacting device 2, and the pH of the circulated solution is adjusted to 10.5-11.5. Consequently, the solubility of Na2O in the circulated solution is raised and the elution of SiO2 is prevented. When the pH of the circulated solution is < the lower limit, the solubility of Na2O is reduced, and when > the upper limit, the amount of the elution of SiO2 becomes too much, and the filtering characteristics of the insoluble residue is deteriorated.</p> |
