Method for separation of solid mixtures by simultaneous multi-stage

Abstract

A method for separating a desired component from a solid mixture by repeated recrystallization in a single vertical crystallizer having a plurality of chambers partitioned by solid-liquid separation means, which comprises intermittently feeding a solid mixture to the top chamber and a solvent to the bottom chamber, dissolving the solid in each chamber in the solvent by heating after feeding of the solid mixture to the top chamber, transferring the resulting solution in each chamber to the adjacent lower chamber while taking out from the bottom chamber the solution from which the desired component is recovered as an end product, cooling the solution in each chamber to precipitate crystals, and transferring the resulting mother liquor in each chamber upwardly through the separation means not capable of passing the resulting crystals by the feeding of the solvent to the bottom chamber, while allowing excess mother liquor to overflow from the top of the crystallizer, the above procedures being repeated continuously. The crystallizer suitable for practicing the method is composed of a tower having a feed port for feeding the solid mixture and a discharge port for overflow of the excess mother liquor in the upper end portion, a feed port for feeding the solvent and a discharge port for taking out the solution in the lower end portion, separtion means for separating solid and liquid by which the tower is divided into chambers, and means for heating and cooling the content in the tower.