Patent ID: 7017367

Claim:
A method of controlling progressive freeze-concentration, said method comprising the steps of: circulating a cooling medium through a cooling-medium flow route of a freeze-concentration apparatus while circulating a target liquid for freeze-concentration through a target-liquid flow route of said freeze-concentration apparatus, thereby gradually forming ice crystals on wall surfaces of said target-liquid flow route in freeze-concentration of said target liquid; connecting to said target-liquid flow route a volume expansion detecting means for detecting volume expansion of said target liquid; obtaining thickness of said ice crystals in said target-liquid flow route from volume expansion detected by said volume expansion detecting means; and controlling flow rate of said target liquid and growth speed of ice front in said target-liquid flow route to become equal respectively to a set flow rate value and to a set growth speed value by carrying out Operation A and Operation B based on said obtained thickness; wherein said Operation A comprises calculating inner diameter of said ice crystals in said target-liquid flow route from said obtained thickness, calculating a required flow volume of said target liquid in said target-liquid flow route from said calculated inner diameter and said set flow rate, and adjusting circulation volume of said target liquid such that measured flow volume of said target liquid inside said target-liquid flow route becomes equal to said required flow volume; and wherein said Operation B comprises calculating actual growth speed of said ice front in said target-liquid flow route from said obtained thickness and adjusting at least one selected from the group consisting of temperature and circulation volume of said cooling medium such that said calculated actual growth speed becomes equal to said set growth speed value.