Crystallization of phosphogypsum in continuous phosphoric acid industrial plant

Understanding crystallization of phosphogypsum is generally of basic importance for industrial wet-process phosphoric acid production. In this paper, measuring the phosphogypsum crystal size distribution during primary and secondary nucleation is reported. The results show that, secondary nucleation was occurred at 5 hr run time (12.5% solid content). Crystal growth rates were about 18.4 mum/hr at 2.5% solid content and about 4.5 mum at 30% solid content. At steady state (16 hr run time and 30% solid content), the mean diameter of the crystals and the average specific surface area are about 25 mum and 0.69 m(2)/g, respectively. (C) 2004 WILEY-VCR Verlag GmbH & Co. KGaA, Weinheim.