| 摘要 |
<p>1290471 Reflux crystallisation VERENIGDE KUNSTMESTFABRIEKEN MEKOG ALBATROS NV 8 Jan 1970 [10 Jan 1969] 1009/70 Heading B1G [Also in Division Cl] The mixing of ion-containing liquids to produce a crystalline precipitate is effected in a Rotating Disc Contactor (RDC) in which an ascending current is maintained. An RDC is a vertical cylindrical column divided into spaces internally by baffle rings having a central opening, and in which a stirring device is present in the form of a rotatable shaft extending through the openings, and carrying horizontally mounted discs. The largest crystals descend and are recovered, optionally after washing in a second RDC of smaller diameter than, and mounted below the first, and in which a slower ascending current is maintained. A space above the first RDC may be provided in which the ascending current is made slower than in the RDC, e.g. by removing liquid from the bottom of the space. Discharged mother liquor which may still contain fine crystals may be recycled and used for dissolving initial materials. The following crystallizations are exemplified:- (1) mixing of crude phosphate containing 50% CaO + 35% P 2 O 5 , dissolved in HNO 3 , with H 2 SO 4 giving double decomposition into calcium sulphate hemihydrate; (2) the reaction H 2 SiF 6 + 2NaCl (or 2KCl) -> Na 2 SiF 6 (or K 2 SiF 6 ) + 2HCl; (3) the successive reactions (a) 2MgSO 4 + 2KCl + 6H 2 O -> MgCl 2 + K 2 SO 4 .MgSO 4 .6H 2 O, (b) K 2 SO 4 . MgSO 4 .6H 2 O + 2KCl -> MgCl 2 + 2K 2 SO 4 + 6H 2 O. In (3) above, each reaction is conducted in an RDC, precipitation being effected in reaction (b) by addition of, e.g. methanol, ethanol, dioxane or acetone.</p> |
