Investigation of Countercurrent Crystallization Purification Apparatus

Abstract

Fractional crystallization has not been as widely used commercially as its potential value as a powerful separation tool justifies, because equipment has remained undeveloped and inefficient and distillation has usually been used. In exploring a new approach to the development of more efficient equipment, a crystallization purification column was developed which produces a high purity product by continuous countercurrent treatment of the crystal mass with some of the melted crystal product.We investigated this countercurrent crystallization purification apparatus, and analysed the various phenomena in the purification processes: i. e. the relation between the falling rate of porous piston and the heat supplied at the bottom of the column, the effect of pressure on the purifying capacity of the equipment, temperature distribution and concentrations of products. The transfer processes of heat and mass in this column were analysed by a simple model for the crystallization process, and experimental results were compared with the theory. From these results the transfer coefficient and H.T.U. of this column were estimated.