Kureha Kagaku Kogyo Kabushiki Kaisha

Takeshi Imura

Shigeru Saitoh

Masaaki Shimada

Crystals containing a molten liquid at the bottom of a purifying tower are cooled, so that three effects i.e., washing, sweating and recrystallization are improved while maintaining a heat balance within a tower to thereby obtain highly pure crystals. The apparatus according to this invention comprises a crystal purifying tower of a transversal cross sectional configuration in which two circles are partially joined to each other and in which a stirrer having blade members spirally attached around the surface of a rotational shaft is disposed at the center for each of the circles, the purifying tower having a starting material feed means about at the middle thereof, a heating means and a product take out port at the upper portion thereof, a cooled crystal feed means, a low purity crystal component take out means and a means for extracting a portion of the crystal component at low purity out of the system at the bottom thereof, wherein the crystal component at low purity taken out by the low purity crystal component take out means is crystallized and then cooled by a means disposed outside the purifying tower for crystallizing and then cooling the crystal component at low purity, and the crystals thus crystallized and then cooled are fed by means of the cooled crystal feed means to the purifying tower.

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Iwaki, Japan

Takeshi Imura