BENEFICIATION OF UNWEATHERED INDIAN CALCAREOUS PHOSPHATE ROCK BY CALCINATION AND HYDRATION.

Unweathered low-grade calcareous phosphate rock of about 20 percent P//2O//5 grade was beneficiated by a procedure in which contained carbonates were decomposed by calcination at about 1,000 degree C. On quenching the hot calcined rock in water, major impurities passed into a slime phase which was mechanically separated from a coarser concentrate fraction. Phosphate rock of two major types was beneficiated in batch-scale studies yielding concentrates containing 31. 3 to 38. 5 percent P//2O//5 at recoveries ranging from 54. 8 to 86. 0 percent. The samples were from two major deposits in India. Processing information gained was utilized in extending the work to a continuous-flow system, processing phosphate rock at rates up to 157 kilograms per hour. Superphosphate exceeding 16 percent water-soluble P//2O//5 was prepared from concentrate derived from continuous-flow processing. The work described was performed in India in 1968-70, where the author was assigned as an advisor in extractive metallurgy to the Indian Bureau of Mines laboratory at Nagpur, Maharashtra.