METHOD OF REFINING CRYSTALLINE MATERIAL

摘要

A method of refining a crystalline material, comprising charging from above a feed raw material crystal containing impurities in the solid form into a columnar continuous crystallization refining apparatus equipped with stirring means, melting sedimented crystal by heating means provided at the lower part of the apparatus, bringing the crystal into counter-current contact with the resulting molten solution for refining the crystal, withdrawing the crystal thus refined from the lower part as molten solution and withdrawing a mother liquor containing concentrated impurities from the upper part, wherein the feed raw crystal or the column upper part of the continuous crystallization refining apparatus is heated, or the mean grain diameter of the feed raw crystal is regulated to be at least 2.5 mm, so as to keep the temperature of the mother liquor existing on the upper part of the apparatus within a predetermined range, whereby it is possible to form an excellent crystal and a slurry layer inside the crystallization column even when the properties of the crystal are relatively inferior, and provide a crystal product having high purity in a high yield.