The mechanism of purification by continuous multistage countercurrent fractional crystallization has been studied. For a low eutectic system

countercurrent washing plays a main role in purification. The mathematical model which describes the impurity concentration vs. the crystal bed height in the purification column is as follows The influences of operating variables such as feed composition

reflux ratio

height of crystal bed and agitation intensity were studied theoretically and experimentally as well. A purification column 50 mm in diameter and 1060 mm in height was used in the experiments.The experimental results indicate that all the variables have important influence on column performance and the mathematical model gives results in good agreement with the experimental results.