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Crystallization of High Purity Ammonium Meta-Tungstate for Production of Ultrapure Tungsten Metal

Cheong-Song Choi^† Jun-Hyung Kim¹ Choul-Ho Lee²

Dept. of Chemical Engineering, Sogang University, .P.O Box 1142, Seoul, Korea ¹Agency for Defense Development, Taejon 305-600, Korea ²Dept. of Chemical Engineering, Kongju National University, Kongju 314-701, Korea

cschoi@sogang.ac.kr

Korean Journal of Chemical Engineering, November 2000, 17(6), 643-648(6), 10.1007/BF02699111

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Abstract

The growth mechanism of Ammonium Meta-Tungstate (AMT) crystal was interpreted as two-step model. Growth rates of AMT crystals were measured in a fluidized bed crystallizer. The effects of temperature, supersaturation and crystal size on the crystal growth were investigated. The contribution of the diffusion step increased with the increase of temperature, crystal size and supersaturation. The nucleation kinetics from measurements on the width of the metastable region of Ammonium Meta-Tungstate (AMT) was also evaluated. The crystal size distribution from a programmed cooling crystallization system was predicted by the numerical simulation of a mathematical model using the kinetics of nucleation and crystal growth. It was also observed that the shape of AMT crystals was changed during the growth period.

Keywords

Ammonium Meta-Tungstate Crystallization Process Control Crystal Growth Crystal Size Distribution

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