COUNTERCURRENT, COOLING CRYSTALLIZATION AND PURIFICATION METHOD FOR MULTI-COMPONENT MOLTEN MIXTURE

摘要

A countercurrent, cooling crystallization and purification method for a multi-component molten mixture wherein the mixture is treated by a purification system comprising one or more crystallizers (1A, 1B) each having, at the respective upper portion, a clarifying portion (10A, 10B) and a purifier (2) arranged in series to the crystallizer or crystallizers and having, at its upper portion, a clarifying portion (20), the crystallizer or crystallizers and the purifier having a temperature difference therebetween and disposed in the order of temperature. The starting mixture is fed to one of the crystallizers and subjected to crystallization there, and the resulting crystals are taken out from the bottom of the crystallizer and fed to another crystallizer or a purifier of higher temperature while the clarified liquid, i.e., mother liquor positioned at the clarifying portion of the crystallizer is led to another crystallizer of lower temperature or discharged out of the system. In each of the crystallizers and purifier, the crystals are moved downwardly while the mother liquor is moved upwardly to effect countercurrent contact with the mother liquor. Through this countercurrent contact of the crystals with the mother liquor of higher temperature, the crystals are purified by being washed with the mother liquor. With this arrangement, the purification of the mixture can be attained effectively and at a reasonable cost.