| 摘要 |
An apparatus for producing seed crystals in melts has a vertically oriented, closed vessel having a vessel base and having at least one inlet for the melt and having at least one outlet opening for the inoculated melt provided with seed crystals. A preferably annular region of the vessel wall is constructed as a cooling surface. In the interior of the vessel there is arranged a scraping unit which comprises a motor-driven rotating shaft which extends axially through the vessel as far as a point just short of the vessel base. At its end towards the vessel base, the shaft is provided with at least one scraping arm which, starting from the lower end of the shaft close to the vessel base, extends first in the direction towards the vessel wall and thence substantially parallel to the annular cooling surface and axially parallel to the drive shaft. On the scraping arm there are preferably arranged one or more scraping blades which during operation sweep along the inner wall of the vessel in the region of the cooling surface. The scraping unit is heatable. The production of granules, especially of high molecular weight, for example >300, is carried out in a crystallization plant which comprises a supply container for the melt, an apparatus of the afore-described type for producing seed crystals in the melt, and a prill tower in which the inoculated melt provided with seed crystals is sprayed or introduced dropwise into a cooled current of gas. The drops crystallize during their free-fall descent. The granules so produced are discharged at the base of the tower.
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